Hi, to be honest my computer probably has a serious problem. When I try to start up Windows normally, I type in my password for the user account and then it just freezes, it doesn't load. So I think, okay, I'll just try to start up it in Safe Mode, no problem. But when I try to start it in Safe Mode the computer freezes at classpnp.sys and doesn't continue. I'm at a loss about what to do (not that computer savvy, so plain terminology please) My computer is a Gateway Desktop, running Windows 7 Home Premium (64bit), intel premium processor, 1 TB hard drive, 6 GB DDR3 memory. I tried using the "Last Known Good Config" option, to no avail. I got the "Replacing invalid security ID" message. I let that go for about an hour when I stopped it, as it was going nowhere. If it makes any difference, I have also installed another operating system (Ubuntu).