The comp:
ASUS motherboard, M3A76-CM
AMD 6000+ dual core CPU
4 gig RAM (2 2g sticks)
Win 7 Pro x64

I replaced the motherboard in this comp some time ago, last June maybe. I was running a release candidate of Win 7 until it recently expired last month and got a copy of pro x64. Shortly after I noticed the computer randomly restarting itself after a few hours, though with no real pattern. It then started freezing randomly and semi-rarely, though again with no real pattern. One night after restarting the mouse (I use the mouse that came with my Wacom tablet) became unresponsive as well as the keyboard and anything attached by USB. After a few restarts it stopped for a week but tonight its back, though only affecting the mouse.

It works fine up until I'm past the login screen, then freezes wherever it lies. Unplugging the mouse and reattaching does nothing, and it does it to non-USB mice I tried as well. It does not do it in Safe Mode at all. Problem is I don't even know where to start...I disabled all startup programs but nothing, and I really don't even know how to adequately navigate without my mouse. I'm having to write this from my Backflip.

Any help troubleshooting would be great, but please use lameman's terms...I'm a novice at repair and don't claim to know where or what everything is.

You don't say if you have a Video card and as these tend to hunger for a large portion of the total power output I am suspecting the PSU. Update with further info to see if we can assist more or just spend more here if you know yours is embarrassingly cheap :darth:

I do have a card, a MSI invidia 8800 GTS. Its a couple years old now.

When you changed to 64bit did you update all your drivers and have you done that since?
http://www.nvidia.com/object/win7_winvista_64bit_196.21_whql.html

can you disconnect / remove and use the on-board to check (i) drivers (ii) power usage fault?