First, the issue happened once and then didn't happen again for weeks. Then it started happening more frequently until it now happens within minutes of windows starting.

The problem:

Windows boots normally. After reaching my desktop the PC will randomly freeze without warning. (Mouse doesn't move, program/browser stops suddenly, etc.) The screen APPEARS like a SCREENSHOT of whatever was happening when the freeze occurs.

After a HARD reset, the option appears to "Go to BIOS setup" or "Load Default Values". After choosing option 2, the date is set to 2005 and the usual "Windows did not shut down properly" message appears.

The computer:

HP Pavillion, 2009
windows vista
1 gig stick replaced last year
video card also replaced last year, everything else original parts.

I'm pretty competent on software things, not really that experienced with hardware outside of basic replacement (like a video card). I need help!
Replace the CMOS battery...Part # CR2032 AVAILABLE anywhere...
As always when working inside the PC remove all POWER sources and take anti-static precautions...

See how it goes overnite after this...if it is still freezing randomly DLoad and run SpeedFan and Post all your system temps here.I replaced the battery, started it up, and the same problem is occuring.OK...what about part 2 above ? ?
Post the temps reported by SpeedFan...The problem seems to have worked itself out. After a couple of days, the freezing has no longer happened. Strange result.

Thanks for the help!Good News...strange...but good nonetheless.