I think the system files of windows might be affected. Looking at the support.dell.com website it's eigther you have windows vista or windows XP as your operating system
what you can do is Startup Repair, System Restore
1. To do this you have to boot your computer to the Windows Vista disk
.At the bottom says "Windows is loading files...."The Windows Setup environment will continue to load
2. At this screen you should configure the Language to install, Time and currency format, and Keyboard or input method options so that they are set correctly. When done, press the Next button. You will now be at the main Windows Vista setup screen where you would normally install Vista on to a computer.
3. Click Repair your Computer and keep on hitting next until you get the menu
4. Choose Starup Repair First Keep on hittng next until computer restarts.
5. If it fails repeat steps 1 to 4 and choose System Restore
6. System restore will prompt you choose a date. I suggest to choose a date within a week when the computer's setting is up and running
Hope This helps