Question : cant search a Windows 7 drive when connected to my xp machine via usb

I have a laptop with a virus.  The virus is bad enough it shuts down any attempt to run anything to repair the problem.  I took out the hard drive and connected via USB to my XP pc as usual.  But it only gives me a couple boot folders and doesn't allow me to walk through the whole drive.  Why not?  How can I get access to the rest of the drive so I can scan and squash this virus?

Thanks.

Answer : cant search a Windows 7 drive when connected to my xp machine via usb

Have you encrypted the harddrive in any way? For example have you played with BitLocker?