Help with multiple problems

Hello all,

First time poster, long time lurker....

Lets see, where should i begin... Well, i have a computer that i built about 8 months ago. Anyways, my latest problem is that i have had a linksys wireless card cause a hardware stop blue screen. So to remedy this, i uninstalled the card, went to buy another card as a replacement and the card will not show up in device manager, in either windows xp or vista. I tried a sound card that i know works and it does not show up either. I have tried all the slots on the board as well. So for kicks i reinstalled windows, and was installing updates and such, and now the onboard lan no longer works. Is my motherboard slowly dying or could it be the power supply? I'm at a total loss here with so many problems happening at once on a fresh install of windows.

Thanks for any help!