sfc /scanfile

I went to command prompt as administrator, I tried to type sfc /scanfile="c:\windows\system32\dwm.exe" and then it says "Windows Resource Protection could not perform the requested operation" but it suppose to be says "Windows Resource Protection did not find any integrity violations", any ideas?

My computer specs:
Graphics card: NVIDIA GeForce 8400 GS
CPU: Intel Core 2 Duo E4600
RAM: 2 GB
OS: Windows 7 Home Premium x86 SP1
Model: HP Compaq dc7800 Small Form Factor

AddRAM said:

the command is sfc /scannow

sfc /scannow is working, but i tried other computer, if i type sfc /scanfile="c:\windows\system32\dwm.exe", it doesn't says "Windows Resource Protection could not perform the requested operation"
i need help with my computer to get rid of "Windows Resource Protection could not perform the requested operation" error