can't copy files from sansa to local harddrive in windows 7

[paolo.forest]

i want to copy files (*.mp3) from my sansa c250 v2 (running official firmware, not rockbox) to a local harddrive in my computer
but i can't do it in windows 7
in windows xp or windows 2000, it was all good

in windows 7,
It just pops up a message saying "access denied"
i've verified the security settings, and "everyone" should have full control of those files.

really have no idea how to proceed troubleshootinig from this point