|Might be a virus on the flash or system already, Might be defective software or firmware or hardware.. |
It shouldn't ask for a cd.
Might look for a hidden file on the drive called autorun.inf.
If so read it in notepad.exe. See what it says.
Make a folder on the flash that is called autorun.inf to help prevent if future.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10