The main cause of destruction/modification (wrong) of an operating system (OS Windows XP) are viruses. In most cases, users who have such corrupt files in the system, find solving in formatting and/or reinstalling 
the operating system. Last days I had to solve such a problem and I found a method as efficient as reinstallation, but much simpler and faster.
Replacing corrupt system files with original ones using Sfc.exe ( System File Checker ).
How do we proceed? To repair corrupt files with the help of sfc.exe , it is necessary first of all of cdthe Installation Windows XP in cd/dvd drive . “Start” , yes in “Run…” give the order: “sfc /scannow” (go ” ). The scan starts automatically and the corrupt files will be replaced with the original ones on the CD. At the end of the scan … Restart ! :D
System File Checker Tool Syntax
Sfc [/Scannow] [/Scanonce] [/Scanboot] [/Revert] [/Purgecache] [/Cachesize=x]
More details about Sfc.exe Find on support.microsoft.com (Description of Windows XP and Windows Server 2003 System File Checker (Sfc.exe) )
 
			