|There should be no difference between drag and drop and any other file move/copy.|
Some area of the system is bad.
See event logs, run linux or barts live cd and see if you can reproduce. If so at least we know hardware.
Consider diag suite.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, Make an autorun.inf folder on all usb drives.