If your Operating System Failure,Here  is the method:

1, To start under “safe mode”
When the system frequently fails,the easiest way is to start the computer in Safe Mode.

2 To restore the previous registry
If there is a more serious problem, it may wish to adopt to restore the registry before failure.When the system can not be windows, with windows startup disk and boot to MS-DOS, the DOS prompt, type scanreg / restore, and carriage return, will show the registry files backed up and restored.

3 Checking critical system files
If the system failure has been exited,now suddenly appeared the problem,at this time  restored in the registry is useless,because the problem is even earlier than the system self-built. Well, this is the system files caused damage,may be many reasons, such as applications overwriting important system files, or disk damaged system files, such as. Vxd. Dll and so on. User does not accidentally delete the system files fatal,run System File Checker, if detected errors,it will be prompted,then you can put into install CD-ROM and it will be restored.

4 Uninstalling the conflict equipment
Enter Safe Mode, open the Device Manager to uninstall the conflict hardware.
 
5 Quickly coverly install
For beginners and less experienced maintenance personnel, they want to retain the original windows but can not enter the system setting ,atthis time they can use quickly coverly install,if the above method is still not solve the problem, they have to Format the C drive, reinstall the system.