Vista x64 Loses Video settings - can't display

Gang I have a very puzzling problem - just one - on an otherwise healthy HP minitower running Vista Home 64-bit. It has an older low-end embedded Nvidia gpu - not very potent. The symptom here is simple: Vista boots/loads normally, I get the POST screen, can deal with SETUP, Safe Mode works, all that is good, but when the User's account loads and it goes to setup the display settings, instead of the nice desktop I get a pattern on the screen that looks like > > > > arrows arranged in a diagonal pattern, static. In other words, its not "noise" its a pattern. If I instead boot the the "clean" account that I use for working on it, it looks fine. Twice I have uninstalled the video device, cleared out all the driver stash, reinstalled fresh with latest Nvidia [whatever WAS the latest/last for that device] 'ware, and things are peachy. Wait a week, and the problem is back.

One other thing to note is that I have noticed in playing with different resolution settings, that Vista will not always "hold" the resolution I give it and that bothers me... I thought that perhaps there was one mode, unfortunately the "native" one for the monitor, which was having difficulty sync'ing or something, so I would deliberately set a non-native mode and refresh rate, but on a reboot, that one would no longer be valid and it would default to a different mode.

The first time I did cleanup on it it did have some routine malware, and on a subsequent scan, I used TDSSKiller which claimed one positive, resolved it, and came up clean on subsequent scans. But during these steps, the display was fine. afterward it was fine. I leave, get a call a week later that the display is whacked again.

Does something in Vista itself need R&R ? Ideas??