it's likely you have some corrupted files...there are a number of ways to resolve...do you have the Windows setup CD? If so, you can try a windows repair by booting from the CD...

Pro or Home?
You on a domain?

please elaborate more in detail...

Thanks for your reply.

Can you please guide me that how I can repair windows by booting from CD. As I have tried and it opens a console where it asked to enter windows driver. after this it shows:

F:\Windows (As I installed windows in F drive)

After this it did not shows any progress? wht command i shld right here in order to repair windows?

Regards,

Thanks for your reply.

The problem is that system restarts and after this it gives an error:

"A log off error has been occured"

I searched for this error and got one answer that i shld test my system's RAM. But I am not sure abt this solution. 2/3 days ago I installed a new printer. Is this new installation linked with this log off error?

Regards,

"A log off error has been occured"

this is not even proper English ,where did you get the error from !

You can see the screen shot of this error.

Regards,

thats not "log off" thats LOG OF !!!!

can you check the event viewer to elaborate on the error.
start/control panel/ administrative tools/computer management/system tools/event viewer.
Look for anything with a yellow or red symbol and then double click. It should tell you the error and some infomation to help find the problem. It could be as simple as a printer service set up in your user account which needs moved to all users.