Try using the Full free version of Grisoft's AVG virus scanner from
www.grisoft.com. Before downloading I would recommend turning off system restore in the system properties, system restore tab.
Once it is installed, boot into safe mode and pull up a command prompt.
Type in the following to enter into its 'DOS' based scanner, and see if it helps.
C:\progra~1 (enter)
cd grisoft (enter)
cd avg6 (enter)
avg (enter)
This free tool has saved my bacon many times. We also have recently used a tool from pcguardian if I remember correctly.