Thanks for getting back to me and yes it's very aggravating!! I may have solved my problem. I forgot to mention my PC dual boots Xp and Vista. I set up Xp first (seems easier that way) and never really did much with it other than use some older programs that won't play nice with Vista. After installing Xp, I used Partition Magic to create two other partitions on my new drive (through Xp). One was for data (the one I can't access) and Vista.
After posting last night it dawned on me that I've never been booted into Xp, and tried to connect to the network drives from another PC. So I did, and in Xp, nothing was shared! I shared all the drives I wanted to use, rebooted to Vista, and now all is well in my Windows world- GRRR!
I suppose Xp had put a "marker" on the inaccessable shared drive not to share it, and it must take presidence over Vista as Xp was the first to see the drive.
I don't know if you have any other OS's on your computer, but if you do, try to see if they can share the drive.
I'll have to think out the file transfer issue. Sounds like a network issue more than a Vista issue. I don't have any trouble with errors and large files.
Thanks again for your time,