AGP videocards may use an 'AGP lock' at the back of the socket to hold the card in place, so check to make sure it is unlocked before focing anything. Both the AGP, PCI, and ISA (if your computer is really old) card should pull out without too much effort. Next, remove all the screws which attach the motherboard to the case - there should be about 5 or 6, but there may be more.

Leave the processor and memory in place, it is easier to remove these items when the motherboard is out of the case altogether.

With the motherboard unscrewed from the chassis, gently remove it from the case and place it on a hard surface. You can now remove the heatsink, processor and memory from the board if you need them for the new motherboard you're just moments away from installing. Removing the memory simply involves opening the pair of clips that holds each memory module in place.

The method for removing the heatsink and processor varies depending on their make, and model.

Intel Pentium 4 processor heatsinks use a pair of latches which can be released to enable the device to be removed from the retention frame. If you have an AMD Socket A processor, you may need to use a small flat-head screwdriver to remove the heatsink. In this case, slot the screwdriver into the flange on the heatsink's clip, and press firmly down and away from the processor slot until the clip comes free.

If your processor uses the older Slot 1 or Slot A form factor, there may be some tabs on the outer edges of the processor package which need to be pushed in before the CPU can be removed from the slot. In any event, it shouldn't take much force to remove the processor from its socket, so if you're meeting resistance, stop and double check for a clip, clasp, or lock of some sort.

For modern Intel and AMD processors which use sockets, once the heatsink is removed, opening the lever on the CPU socket will release the processor. Pull it off the board gently and store it in its original package if possible, or pins down on an anti-static bag or similar surface if not. If you don't intend to reuse the processor and memory from your old motherboard, it's easiest to just leave it in place for storage.

With the old motherboard removed from the case, I highly recommend giving the inside of the case chassis a quick wipe down with a dry cloth to remove whatever dust has accumulated.

An even better way to spring clean the inside of your case is with a can of compressed air from your local computer, electronics or hardware store. It's best to have the computer outside, or in an area that can be easily vacuumed afterwards, as cleaning with compressed air can generate a lot of loose dust and assorted airborne gunk.

Thoroughly clean the inside of the computer of all visible standing dust using the compressed air. Be sure to hold the can as close to vertical as possible to prevent unnecessary liquid spray. Be aware of your health too, since when you first let loose with the compressed air, you are going to create a huge cloud of nastiness which you want to avoid breathing in. Goggles might be a good idea here too. Generally speaking, you are simply trying to remove as much of the visible dust as possible.

Now your system is ready for the new motherboard.