OK, pre-upgrade I was running 10.5.8 on my Mac Pro, and I had file letters mapped in Vista to all of my Mac Pro's drives. Post-upgrade, I can no longer connect to any of the drives -- I can see the Mac Pro in my Network window in Windows, but double-clicking on the Mac Pro results in a password prompt in which no password is accepted. Obviously something has changed on the Mac. I've gone through the Network dialog boxes in 10.6, but can't find any culprit. Anyone have any ideas?