Do I need a new display adapter?

I have a XPS 410 (same as Dimension 9200) with Vista and a NVIDA GeForce 8300 GS display adapter.  Everything ran flawlessly for years until recently.  Now I can't boot up unless the GeForce 8300 GS display adapter is disabled or uninstalled.  If it is enabled, on startup the system goes through POST successfully.  But as windows begins to start up, the screen suddenly goes blank and the system reboots.  After going through the same thing again, the screen goes blank and there is no sign of life on the hard disk.  Or sometimes it goes to the "repair your computer" screen and waits for a response.

If I go into safe mode and disable or unintall the GeForce 8300 GS display adapter, windows will then start up successfully and everything works the same as before, including audio.  Except for the display.  It looks like I'm in safe mode -- everything is fuzzy and oversize.  I'm assuming it's because generic drivers are being substituted for the usual ones.  The monitor comes up as "default monitor."

This problem came up suddenly and it did not happen after the installation of new hardware or software.  I took my computer to a repair shop where it passed every diagnostic they ran.  Their solution was to format the hard drive and reinstall Vista, which was OK with me.  But it didn't solve the problem, even after I reinstalled all the appropriate drivers on the Dell support site.  I eventually restored a Norton Ghost backup copy of the disk and reinstalled the drivers again.  I even went to the NVIDA web site and installed their latest driver for the GeForce 8300 GS.  It didn't solve the problem.

When I enable the GeForce 8300 GS display adapter, the device manager lists it correctly and it looks normal.  But I can't reboot successfully until I disable or uninstall the display adapter.   I've tried everything except a new display adapter.  Do I need a new display adapter?  Any advice you could offer would be greatly appreciated.