If your Windows Vista computer is acting unpredictably, the most likely culprit is bad memory in your RAM. Without Vista, it's pretty easy to perform a diagnostic test of your memory to either rule this out as a suspect, or to find out that this is the cause of your problems.

To start insert the Windows Vista DVD in your drive and reboot your system. Before the system comes up, hold down the space bar and continue to hold down the space bar as the system boots up. By holding down the space bar, you'll get taken to the Windows Boot Manager. Use the Tab key to select the "Window Memory Diagnostic" option at the bottom of the screen. Once it is highlighted, press Enter to start the memory diagnostics. The test itself is pretty much automated. Once it starts you wait for it to tell you if you have a problem or if everything is fine.