Apologies if this has been answered before,On my Vista Ultimate 64 bit PC, I have set up sharing as follows ....The whole of the D drive (local disk)K drive (external drive).... as part of the HOME newtwork and set to private.I set up HOME network on my XP laptop. I can map a drive a drive to the K drive no problem and access the files.I can map a drive to the D drive, but when I try to acess the drive, I get permission denied.All sharing permissions on both drives are identicle.Password protection is turned off in Sharing and Discovery Thanks in advance !

Try to disable and re-enable the file sharing on D drive again. You can also check this simple file sharing in Vista to see any misconfiguration.