SFC /Scanonce
Scans all protected system files once.
To scan the system files once, do the following
- 
				Open Command Prompt (Be sure to open command prompt as administrator. The instructions for Command Prompt will tell you how to do that) 
- 
				Type SFC /scanonce (There is a space between the SFC and the /) 
|  | 
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				Press Enter 
NOTES:
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				You must be logged on as member of the Administrators group to run sfc. 
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				If sfc discovers that a protected file has been overwritten, it retrieves the correct version of the file from %systemroot%system32\dllcache folder, and then replaces the incorrect file. 
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				If the %systemroot%\system32\dllcache folder becomes corrupt or unusable, use sfc /scannow, sfc /scanonce, or sfc /scanboot to repair the contents of the Dllcache directory. 
