I am running Windows Vista and have not had any problems until the last 2 days...only thing I remember happening recently was getting an update from Adobe Acrobat, otherwise I have not downloaded or installed any new programs. System will operate great for about 30-60 minutes and then it locks up. I can't click or open/close any programs that are currently running, leaving my only option to turn the system off altogether. When I fire it back up, I am given the option to start Windows normally or in safe mode. Normal mode works great for 30-60 mins and then I am right back to shutting the system down.