If disabling UAC did it, cool. If not, don't worry about memtest; we can test the memory this way instead:
1. Reboot and enter the Advanced Boot Options menu by repeatedly pressing F8.
2. Once in the menu, do you see a Repair Your Computer
item on the list? If so, select it. If not, skip this list and go to the alternate method below.
3. Select a keyboard layout, and then click Next.
4. Select a user name and enter the password, and then click OK.
5. On the System Recovery Options menu, click Windows Memory Diagnostic
If Repair Your Computer is not listed, you will need your original Windows Vista installation CD.
1. Insert the Vista CD and reboot.
2. If prompted, press any key to start Windows from the installation disc.
3. Choose your language settings, and then click Next.
4. Click Repair your computer.
5. Select the operating system you want to repair, and then click Next.
6. On the System Recovery Options menu, click Windows Memory Diagnostic
Let it run and when it's done, your system will reboot and you will be notified of the results via a popup in the lower-right hand corner of the screen. At least once this is done we can rule out any possible memory issues.
Edited by othersteve, 18 November 2009 - 12:42 PM.