Thumbs.db is a file the system create for thumbnails yes, but before a while I have work on a computer which was infected with a virus which uses autorun inf files in disks, I have formated the drive C and I know the virus must have put it self on autorun on all the other drives, and as always I thought I can right click on the other drives and click on open, this will prevent excuting the commands in autorun file, then I can clean the disk, but the virus have corrupted the new system right away after I opened the drive D, I have study how that happen, and it was the thumbs.db, thumbs.db contain commands just like the autorun.inf, and the virus uses a thumbs.db which created by it to corrupt everything might be used to remove this virus, the thumbs.db works like autorun.inf. The setuation on that time did not allow me to keep a sample of this virus to study how to reverse it, but I think disabling thumbs caching and search on any thumbs.db files and delete them on any new removable storage disks before opening them will prevent this virus from re infecting the system, FOR NOW.