|Sounds to me like you've got an autorun worm running on your machine. Firstly, if you haven't done so already, disable autorun:|
Once done, open an elevated command prompt and run the following:
attrib -s -h <drive letter>:\* /s
This will remove the hidden and system attributes from all files and folders within that file system.
Now, locate the autorun.inf file, and open it in notepad - you'll see a reference to an executable, I suggest submitting it to your AV vendor for analysis.
Once this is done, delete the autorun.inf and the malicious binary, then check your common registry load-points for anything out-of-ordinary, and, if you're confident enough, remove it, else, submit an autoruns log file (in the .arn format).