nVidia Driver Problems, HELP!!?

Please excuse me, this is a bit long.

My work computer suddenly just started to have problems since yesterday, the computer would lockup and go to blue screen after certain programs were run, such as AutoCAD. the blue screen said its a driver issue, nv4_disp. I tried to restart the computer but the computer would go into blue screen every time it leaves BIOS and enters windows.

After a few fails I got into safe mode, got into the admin account, and removed the Nvidia display driver. restarted, got into windows no problem, and installed the latest Nvidia driver that works with my video card. Not even done installing the driver, specifically when it installed the nv4_disp file, the computer froze, blue screen, and crashed. back to safe mode, removed the driver.

I tired a different driver from nVidia (slightly older) with the same results- windows lockup & blue screen after installing nv4_disp, can't do anything, uninstall in safe mode.

the office computer admin is currently not available right now (he's on vacation) so I need some serious help.

I'm not quite sure what to do, but I know i must have that driver working again in order to do my work. without the driver the computer barely works, serious lag even when I try scrolling down a text-only web page.

There is no way I can do CAD work or basic word processing like this.

Anything have any ideas?

computer specs:

CISNET, desktop unit, circa 2004

Microsoft Windows XP Professional x86 (32 bit)

inland nVidia GeForce FX 5500 AGP graphics card (was my old home computer's GPU for 5 years)

the computer does have a onboard GPU, SiS ????, its not great, worst case scenario, I'd have that to go back on.

nVidia driver history:

175.19 - previously installed

175.19 - new driver installed, direct download from nVidia

93.71_forceware_winxp2k_english_whql - old driver I tried too.

the 153 and 175 versions is known to have problems with my graphics card and windows XP. that's because it's happened before. roll back to the 93.71 and everything is fine.

but this time it didn't do anything at all.

Now what??