I've seen a few problems identical to mine, except the fix seemingly isn't allowed. I'm hoping for some guidance.

I have a WD800 HDD from my previous desktop I'm trying to access (Win 2000).
I bought an IDE/USB adaptor and plugged it into my new desktop (Vista.) All seems to be working (disk spins up, new hardware found, USB mass storage device ready) but the drive doesn't show up in "My Computer."
It does show up in both Device Manager and Disk Management. In Disk Managment is shows up with no drive letter.
The previous fixes I have seen suggested changing the drive letter and that seemed to solve it.
That where my problem starts - right-clicking only gives me the option "delete volume." The "change drive letter" is there but grayed out and inaccessible.
I do have admin right under both OS's.

Any help would be appreciated.
Thank you