Is this a virus? and ihow do i remove it?

i am using a computer running windows 7 professional. recently i used a flash disk and thereafter i realised that the following folders ($recycle.Bin, Document and Settings, MSOCache, Recovery, System Volume Information) in drive C have a lock indicator infront of them and when i open them i get an error :access is denied" i also realised that in all my folders there appears a file named desktop.ini