This is taken directly from the UAEHowTo.txt included with WinUAE:
"Select the hardrive in page harddrive with add harddrives. If there is no Drive listed then it is possible that this drive has no Amiga/Amithlon Partition or you use win98-me and your ASPI Manager support no Hardrives. The device name for this is uaehf.device."
Regardless of which operating system you're using (Windows 98/Me or Windows 2000/XP), you should download and install Adaptec's
Windows ASPI Package. WinUAE needs an adequate ASPI layer installed to enumerate your system's devices. You can select your Amiga drive from the Hard Drives tab of the WinUAE Properties dialog by clicking on the Add Harddrive button and locating the Amiga drive in the Harddrive drop-down list. Any disk with a valid RDB should be visible, even if the disk hasn't been partitioned.
If everything's working properly, you can use HDToolbox and the uaehf.device inside the emulation to view or edit your drive's partitions:
hdtoolbox device=uaehf.device
If partitions exist on the drive, they should be recognized by Amiga OS.
Trev