Case: Reusing a case is a good bet, unless it has a backplane or is proprietary in some other way. If your old case is a Compaq, IBM, Gateway 2k, or Packard Bell you will probably need a new one.
Video card: This is a good component to save if you're trying to save money, as long as it uses the same bus.
Monitor: Almost every VGA monitor is reusable, especially if you're keeping the video card. Memory: 72-pin FPM RAM can be used in over 98% of all new motherboards. If you want to try the "SIMM stackers" for your old 30-pin SIMM's you may be in for a lot of extra installation difficulties unless you have some brand new RAM to try, too.
Software: Have a bootable floppy disk, and perhaps a hard disk on hand for the installation. Windows 95 is a good OS if want to test your PC's components in a PnP environment.
Hard disk: Almost all hard disks are reusable. If you get another hard disk, save yourself some trouble and attempt to get the same brand. I have an old Conner hard disk that can't work with other brands.
Modems, speakers, CD-ROM's, sound cards, and SCSI controllers are reusable. The major problem you could run into is bus (slot) type. VESA Local Bus slots are extremely scarce, except in 486 motherboards.
High quality brand names of [personal computer] industry leaders: 3Com, 3M, Hewlett Packard, NEC, Seagate, and U.S. Robotics.
Sony, Panasonic, AT&T, DEC, IBM, Mitsubishi are known in other industries, but I don't give them the same respect as the ones above.
Notable mentions are: Adaptec, Altec Lansing, ATI, Creative Labs, Diamond, Fugitsu, Hayes, Intel, Logitech, Motorola, TI, and Western Digital.
Install the CPU
Pentiums, Pentium Pro's, and most 486's are [almost] no-brainers, since you will bend a pin unless you put it into the socket properly. Look at its gold pins: they will have an asymmetric pattern, and so will the socket. But whatever the chip, match the notched corner of the
CPU with the notched corner of the socket.
Since you almost certainly have a ZIF socket, lift the handle 90 degrees, insert the CPU, and then return the handle back to its locked position.
For the Pentium II, I must admit that it is a huge pain in the butt to install. I should soon make a separate page for Pentium II owners. The good thing is that the CPU and the motherboard will have directions. The bad thing is all of the plastic parts that come with both, reminding me a lot of a model airplane. I can't believe a $1700 CPU would use model airplane parts to install, but yet I'm convinced Revell made this junk.
Install any DIMM memory like cache or SDRAM, or DRAM if you have it. Make sure pin 1 lines up to pin 1. 168-pin DIMM's are keyed to prevent you from using the wrong type.
Note pin 1 on the SIMM, and find the pin 1 mark on the motherboard. 72-pin SIMM's are difficult to install wrong, but it's possible if you're extremely persistent and oblivious to your error.
Typically, a hard disk controller will be placed in the farthest right card slot, to be closest to the drives. Typically, the video card will be placed as far to the left as possible.
Always leave gaps (wherever possible) between boards for clearance and being able to view the board without uninstalling it. You may want to install all of the cards now to see how they will look and see where the cables will run. Punch out the holes on the back of the case (if necessary) where you want the boards to go, or alternately unscrew the card slot blanks that cover the slots at the back of the case.
If you have blanks for the holes and you feel compelled, you could punch out all of the holes (or seven or eight of them, depending on how many card slots on your motherboard) at the back of your case.
You don't want to leave gaping holes, so make sure you have the blanks! If the motherboard is to be mounted using plastic inserts, determine which holes will be used. Chances are, your case will have over a dozen holes, some of which should line up with your motherboard when you place it inside the case.
You may want to temporarily install a card (such as a video card or sound card) so you can line up the card with one of the holes punched out in the back of the case to give you an idea of alignment. Keep an eye on the keyboard connector hole. This must line up, or you are in a world of hurt. (AT motherboards only)
Insert plastic inserts into the motherboard's tiny holes where they will slide into the case's slots. If you are using some screw mounts, make sure now that they will align with threaded holes in the case.
Find the hex-shaped brass or steel standoffs that should have come with your case. You will screw them into the case, and then insert a small screw through the top of the motherboard into this standoff. You should use a small washer on the motherboard whenever you put a screw through it. Cloth and rubber washers are best for this delicate installation. I don't think a washer is necessary on the bottom of the motherboard, however gluing one there can't hurt. I use a washer on If the screws are too large to clear the motherboard hole, you will probably have to enlargen the hole in the motherboard, since you cannot reasonably make the case's threaded hole any smaller. It's not unusual to use both plastic standoffs and threaded fasteners to mount a motherboard.
Mount the motherboard in the case.
You will slide the plastic inserts into the slots in the case and make sure they are firmly in place. Make sure every plastic insert has stuck in the slotted hole before you screw in the finishing screws. Make sure all of the hex-shaped screws are through the hole in the case and do not extend more than a few millimeters.
Ensure all four corners are supported, and that at least some part of the interior of the board has support. I recommend no less than six connections to the chassis. My motherboard has four plastic inserts and two screws. Observe the board to see if it is laying flat - the overzealous installer will try to screw in a few fasteners and warp the board. See if your motherboard can take torture by installing and removing an adapter card.
Use your hand on the bottom of the motherboard for support to see how much it bends during a forceful card insertion. This will also let you see if the motherboard is at the right height and position for a controller card. Plug in the keyboard to see if it fits.
Install SIMM memory if you have not already done so. Start connecting cables and stuff to the motherboard now. Pull out floppy cables, hard disk cables, that PS/2 mouse cable you should have bought, and find those jumper wires for your case's doohickeys.
Install all of this stuff in any order. Just line up those pin 1's to the red side of cables, or for doohickeys (your case's LED and reset switches), use the colored wire as the primary pin. Be sure to find the speaker and install it. It usually is a 4-pin connector with two wires (one red, one black), which can be installed either way on the motherboard.
If your case has holes for COM ports and LPT ports, you can punch these out and save a card slot by unscrewing the connectors that came on the slot-filler strip of metal, removing the connector, and mounting it directly on the case.
Power: this is the most important connection, so DON'T SCREW THIS UP.
The AT-style power connector comes in two pieces, and must be connected properly if you wish to see the motherboard ever work. THE BLACK WIRES MUST BE PLACED TOGETHER WHEN PLUGGING THEM INTO THE MOTHERBOARD!!! Failure to follow this rule will most certainly be the easiest way to fry a perfectly good motherboard.
The one-piece ATX power supply connector is a no-brainer, since pin 1 is a square peg. ATX owners must connect a 4-pin or 2-pin connector from the front of case to the motherboard. A momentary switch is used for ATX motherboards to allow for soft-power, ACPI, and OnNow.
Let's take the speaker connection, for instance. Your case's speaker will have a pair of twisted wires, red and black, that terminate in a 4-pin connector. The speaker connection is not polarized, but to be consistent, the red wire goes on the lowest numbered pin. See your motherboard manual for specifics. Other connectors, especially for LED's, are polarized, so make sure the colored (neither black nor white) wire goes on the lowest-numbered pin or the LED will not work.
Now you should install the video card and hard disk card if you have it. In fact, any Plug n Play cards can be put in if you wish, but other cards should be left out for the time being. Our goal here is to make the computer just barely bootable.
So you will only need a floppy drive, a keyboard, a video card, and a monitor. Hard disks and sound cards can be et aside for now.
Some floppy power connectors are smaller than the standard connector, and most P/S's come with one of these plugs. These connectors can only be installed one way, too.
For data, a flat ribbon cable is needed. It is gray with 34 conductors and a red stripe to indicate pin 1. One end of the cable will usually have a twist in it. The twisted portion connects to the first floppy drive (drive A:). The end farthest from the twist connects to the motherboard or floppy controller. The connector between the twist and the controller connection is for the second floppy drive (drive B:).
The tricky part of connecting the floppy drive is that in some cases, you need an adapter that looks like a PC board edge connector, which is keyed to fit one way. In any case, keep track of pin one and line up the connectors so you don't miss any.