how do I close an unknown utility on c drive

When I try to run defragment I get an error message that tells me to close an unknown utility on the c drive. I dont know how to close the utility. What should I do to find and close the unknown utility.

 

Not enough info to help you really. unknown utility could be anything. It sounds suspiciously like a virus or adware, so scan and remove and viruses or adware off your PC first. You can also try defragging after you boot the PC in safe mode. To get safe mode start tapping your F8 key towards the end of POST when booting, just before you see the Windows logo appear. IN safe mode, any programs not needed for Windows to boot are not loaded.