I've had a problem like that.. it was all messed up and acted strange.
Try this (In windows XP) open a folder and go to:
Tools->internet options->Click view tab->use file sharing should be CHECKED but for now UNCHECK IT. -> click ok->right click your harddrive and click sharing and secruity (or properties, then click secruity) click advanced->first tab should be administrators
If it's not: Click add enter "ADMINISTRATORS" in the text box and push check names then click OK click the check box
Does this for everything.
If I'm correct, you're having a problem I had. Try it, good luck, I hope it works!
PS: Dont forget to change settings back
Windows 7 Pro x64
AMD 965 Black Edition 3.4GHz
ASUS Crossfire III
Corsair 650 Watt
Sapphire ATI 5770
500GB Samsung*2 | 150GB VelicoRaptor 10K HDD
C# Programmer+Web Programmer