ya then u are affected with a virus......if you haven't not already scanned ur PC then do it now....if there is no virus then do the following
Goto Run and type 'regedit'(without quotes)
now navigate to
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\NOHIDDEN
on the right window look for the DWORD 'CheckedValue' and
make its value 2, look for another DWORD 'DefaultValue' and make its value 2
again navigate to
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
on the right window look for the DWORD 'CheckedValue' and
make its value 1, look for another DWORD 'DefaultValue' and make its value 2
Restart your PC and you may now be abale to see the hidden files....
regards
ayush_chh