windows will not let you remove any files that are currently in use.
120+ is an large amount to have "in use", so i would suspect some spyware/malware to be at work. it could be a virus/trojan or just your anti-virus checker files (my AVG uses one or two files which i am unable to delete as they are in use)
im sure someone will come on with instructions for how to check in MSconfig what is running and let you know what is safe to disable.
try running a virus check online via housecall click here
just enter your location and let it install the small virus definition pack and you can then do a full system check.
if you want to check for trojans, try click here 30day trial, it wont delete any trojans but at least it will make you aware of their presence.