In response to another post (yes, I'm just too anxious to respond with the answer that I couldnt' wait for sufficient priv's to reply with the answer) regarding installing JDK and getting an invalid drive error..

Scenario:
- my My Documents is mapped to h:\ at the office
- I have my laptop with my unplugged from the network (so no H)
- I have to authenticate locally to the workstation

For some reason, H: (my home directory) is still embedded in some madness somewhere. I found no way around it, so I mapped a new H to my local machine:
- right click My Computer, select Map Network Drives
- Select the bogus drive letter giving problems
- Map to \\ComputerName\c$ (the drive doesn't need to be shared)
- Run installer again-- voilà!

Hope this helps!

P.S. Admins, please feel free to move this post to that other thread or whatever you think is necessary to close the gap. I realize it's an old question, but it must be a recent enough topic if I couldn't find a response elsewhere in the top 10 Google hits.