this is so weird i can't believe it but it happens

copy a file to a removeable usb drive, remove usb drive, make changes to
file on the usb drive, when the drive is plugged back in, the original file
is replaced with the updated version on usb as well as a backup copy!!!!!!

no windows explorer was invoked for a copy/paste operation

orig file=c:/prog files/intuit/quicbooks/data.dat
backup =c:/prog files/intuit/quicbooks/bac/data.dat
orig file copied to =e:/datafile.dat
e: removed and changes made to file
e: plugged back in
orig file and backup as WERE BOTH REPLACED with updated version on E:
without doing anything else except plugging usb drive back in, and it came
up as E.

this is some xp functionality built in???
i am not crazy, this actually happened

[gadjet]

I've had a similar expereince, not that I have figured it out totally, but I did get as far to understand that the issue is with "sync" or "briefcase", most likely "sync" the automatic routine for keepinf files the same on two computers.