File extensions not visible

On my XP Laptop i can't see any file extension with any of the file. When i go and clear "Hide extension for known file types" under Folder options then it does not stay permanent and i can't see file extensions.

Is there any registry settings i need to check or change? thanks
tech2010Asked:
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supergggCommented:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
Value name   : HideFileExt
Possible Data : 1 or 0
 
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wellholeCommented:
You have been infected with a virus. Run something like hijackthis to figure out what's running on your computer and perhaps it'll even fix it for you.
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stewie123Commented:
I would also run malware removal tools as I agree with wellhole this sounds like a virus.

A few good ones are malwarebytes, SUPERAntispyware, and you should run ccleaner as well.
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tech2010Author Commented:
superqqq: after change registry value to 0 it fixed the issue. I wonder how it happened. Could there be virus on my system? will it now stay permanent?
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supergggCommented:
It is possible that it's a virus.
Do the following:
1.  Update your virus scanner and then run a full system scan.  
2. Run windows update.  You may have to do this multiple times until there are no more updates available.
If you are on a domain then a group policy may be changing the value.
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