StarDestroyer.Net BBS

For some reason, my computer isn't starting into Safe Mode when I set it to. I have XP, so I click F8 when it is starting up to get into the Windows Advanced Options menu, where I click "Safe Mode". Then it brings me to the "Windows is Loading" screen, but for some reason, at that point, it simply restarts the computer instead of going into Safe Mode. Any ideas why?

Does it have anything to do with the free AVG virus scan software, AdwareAlert, or RegistrySmart? I was able to run Safe Mode perfectly fine before installing these, but I don't know if it's those things or something else.

I can get into safe mode perfectly well with AVG antivirus and AVG anti-spyware, so I doubt it's that. I don't know about the other two.