actually i advise u not to use any usb's on ure pc anymore... i had a similar virus or malware enter my pc....it makes ure anti-virus totally uselesss....it shows as if it is working but in real its not....try running virus scans and all see if it helps....and btw to do a chek if its the same virus....u will notice tht evn if u were able to open regedit with a patch next time u restart u wont b able to do it and u will have to reapply the patch... DO NOT USE ANY usb on ure pc....if u have then it has the virus/malware in it....it cannot be formatted....ure best choice is to backup ure stuff on an external Hard disk yes the virus/malware duzunt effect external HD's for some reason...and then reformat and reisntalll windows tht will do the trick....and yeah the same thing happened to my frnd the very day as we were working on a project and the virus deleted his entire mp3 library and video library...targeting the .mp3 and .mpeg format...