I had a Dell Vostro 1720 with bad RAM. It gave me a message when I turned it on that said "resource conflict- allocation error 0x02." Then when Windows XP tried to start it would either bluescreen or say that the file C:\Windows\System32\Config\SYSTEM was corrupted and that I would need to run the repair program on my Windows XP CD.
Fortunately, I was able to run the Dell diagnostics program and it told me that my RAM was bad. But the behavior was peculiar and unexpected- I thought it had a bad hard drive!