What to Do
[*]Copy down the information displayed on the screen, which can be helpful in later diagnostics, and reboot the machine to normal mode, if that's an available option.
[*]If the computer continues to fail, reboot into Windows' stripped-down safe mode. Continuously press the F8 key upon rebooting, and choose the Safe Mode option from the following advanced options screen. This starts up Windows without the extra drivers and programs that usually load during startup.
[*]If you're able to get the machine running again, immediately scan for spyware and viruses, which might be causing the computer failures.
[*]Should a new device or program create a programming conflict, a further option is to use the System Restore Utility, found in the Windows application folder, to revert computer settings to earlier, usable states. Using a restore point rewrites the computer's internal systems, so any programs installed after the last restore point will need to be reinstalled in order to work.
[*]Roll back to earlier versions of hardware drivers or manually remove unwanted programs in the Systems Configuration Utility.
What not to DoDo not repeatedly on and off the power switch.Repeatedly powering up a machine with a bad drive, however, will only magnify the problem and possibly ruin data permanently.
If, upon booting up, that happy computer whir sounds more like a grinding moan, keep the machine off and seek out a qualified technician or data recovery service to salvage your drive.