Hi
I had this problem but got plenty of help on here :-)
UAE sees the hard drive, but you need to start UAE using the command prompt as follows:
C:\insert directory of UAE here\WinUAE.exe
-disableharddrivesafetycheck
all as one command
Then you can select the hard drive in UAE.
you could also make a .bat file to start UAE if you use it with Amiga hard drives a lot.