In Windows 7 there is no user interface to delete Ofline Files cache (CSC cache).  The only way to delete cache is using registry key. Detail steps are given below.
Open Registry editor (Execute Regedit from Run window)
Traverse to the path path:HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesCscParameters 
If Parameters key does not exist under CSC you can create a new node with that name.
Now in the Parameters node create a new registry value with the name FormatDatabase of type REG_DWORD (i.e DWord 32-bit value)
Set the data in this new registry value to 1.
Close registry editor.
Reboot the machine