Since maybe a virus has already infected your system you need to manually restore the hidden files options on explorer
You have to go to Regedit and look for this value
User Key: [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\
Advanced]
Value Name: Hidden
Data Type: REG_DWORD (DWORD Value)
Value Data: (1 = show hidden, 2 = do not show)
In any case you have problems accessing your registry, or registry/commandline editing tools have been disabled, please go to this link
http://www.patheticcockroach.com/mpam4/index.php?p=28