Computer Wont Boot In Safe Mode?

I have a Dell Studio XPS8100 running with Windows7 Home Premium Service Pack1, 64-bit OS.When I purchased it I also had Dell put in a Tv card (Hauppauge WinTv HVR-1250) figuring I might be able to watch some of the Tv Channels from the area where my family lives.Anyway here are the list of issues I have been having over the past couple years. The first issue I noticed was when I went into Windows Media Center and clicked the Internet TV feature or the program, the Windows Media Center program would shut down. So I called Dell and they worked on the issue for a couple of sessions that included numerous hours of my time and might I add the difficulties in understanding the tech, but the end result was that the issue was never fixed and so I just gave up on the tv feature all together and started using the computer to do Cad drawings which is the main reason I had purchased the unit.

Over the next couple of years working with the unit I noticed that once in a while Explorer would stop working and restart itself once in a while, Then the other day I installed a new Cad program and the program would starts itself to the part of the program where I would start using it and then just dissapears of the screen.In the same fashion that Media Center did. So in trying to figure out if I could fix the issue, thinking that perhaps another program might be conflicting with the Cad program, I decided to start the computer in Safe Mode, when I do that the computer boots in safe mode to the Log in window where I have to put my Administrator password and then automaticly restarts itself in Normal mode without letting me put any of my password in.Other things I did was add the title of my cad program to the allow list of the firewall, I have scanned the whole system five times with different Malware and virus program with no virus or infections found.