Help!!
Wait that is why I am here. 
About 2 months ago my computer started to freeze up.  Very random when it would do this and did not seem to matter which program I was working in.  The freeze ups went from every few days to multiple times per day.  I tried doing a system restore to a previous date, but it would freeze up or go though the process and then tell me that it could not restore to the date selected.  I tried multiple DATES.  Then finally it just started freezing up after the bios and driver load.  I could not get to the welcome screen, or start in safe mode.  There had been no new programs loaded to cause this.  I have multiple spyware programs, and scanned with all of them, so did not figure it to be a virus.  I tried to reload windows XP but it would freeze during install.  I changed out the battery on the mobo.  Finally I installed a new hard drive, replaced the mother board, and dropped down from 4 sticks of ram to 1 stick of ram to start testing.  It started RIGHT up and notified me I was missing 1 stick of ram.  I added the 2nd stick.  FOUND 1 of the 4 to be bad.  Loaded windows XP and all the wonderful updates.  Got everything back up and running just fine.  That was about 1 MONTH ago.
Worked GREAT for about 2 weeks
2 weeks ago it starts freezing up again.  Windows explorer does not show my slave drive (this is a new symptom), the system restore does not work etc…   Sometimes it freezes on the driver load, sometimes I get to the welcome screen.  It seems to get further if I leave it sit off overnight then try to work on it the next afternoon.  I am out of ideas, but cannot bring myself to buy a new computer yet.  The processor is the only thing that I have not changed out yet. 
Any suggestions would be appreciated. 
Thank you

Windows XP pro SP2 upgraded to SP3
2 gig ram
2.8 Intel processor
Intel mobo
Sounds like a failing HDD to me...
DLoad and run the diagnostics from the manuf. site...
Run the long test.Thank you for the suggestion. 
That was why I replaced the hard drive the 1st time.  It does the same thing now with the new hard drive. 
I am not sure how I am suppose to down load the diagnostics tool when I can not get the computer to get past the XP screen or the welcome screen, or get it to start in safe mode.  DLoad it on a working machine...
Follow the info at the site for creating a bootable CD.
None of them require Windows to be working as they run the test outside of the operating system...