So, what is this nividia display that supposedly was your problem?
It's likely to have absolutely nothing to do with YOUR problem (and should probably get a thread of its own... Fuzion?)
Um, PLEASE tell me you did a FULL "thorough" disk scan on all the drives on that machine once you found it had a "computer eraser" stuck to its side?
If not, I'm 1) suprised that it went away when you removed the magnet!, and 2) suprise it ran this long without the problem showing up again!
It's EXTREMELY possible you scrambled some stuff on your computer by having a magnet stuck to it! (And by "scrambled" I mean "stuck a mixer into its open skull and ran it for a few minutes/day/weeks - however long that magnet was on there!)
So, before you do ANYTHING else, do a "thorough" disk scan on each drive listed in "My Computer" as follows:
0) Open "My Computer"
1) RIGHT-click the next (for the first, that's be the "C:") drive to be scanned and select "Properties" from the popup - to bring up the "Properties" menu for that drive.
2) Select the "Tools" tab, and then the "Check Now..." button in the "Error-checking" pane.
3) CHECK BOTH BOXES, then select the "Start" button.
4) Go watch TeeVee for many hours / sleep!
5) Upon completion you'll have to select the "OK" button from the "Disk Check Complete" popup.
6) Go to #1, selecting the next disk drive listed in "My Computer...."
If no more drives, you're done!
See if computer behaves better. If not, that's be no surprise to me, because who know WHAT might've gotten messed up.
If possible - and you know how* - you could try a Windows Repair at this point, knowing that you're not trying to fix stuff that's on a corrupted disk drive....
Finally: If you ever do another Disk Check run, uncheck the bottom box or you'll have to sleep through the whole thing again!
*If you really want to try this, I can point you to some good walkthrus, but it's not for the novice computer person.....