Try "System Restore" and restore it to a much "later" date (that is before you got the virus).
If not possible, download "BArtPE" to create a bootable emergency disc(
http://www.pcworld.com/downloads/file/fid,63901/description.html). In BArtPE's environment look for these files "system", "software", "sam", "security", "default" in folder "C:\System Volume Information"
Files are restore points from your Snapshot folder, example:
C:\System Volume Information\_restore{D86480E3-73EF-47BC-A0EB-A81BE6EE3ED8}\RP1\Snapshot
Files from the snapshot folder (of a later restore date) try to overwrite your system files in "c:\windows\system32\config\", respectively "system", "software", "sam", "security", "default" (You cannot overwrite these files if you are in Windows environment, rather in Recovery Console and BartPE)
I already tried these operation recovering from bad system files with regards'--- BSOD.
Hope this helps.
Regards,
George