I use this at work (so I don't have the doc available right now to verify you can remap the Windows key), but it's very powerful. Freeware and shareware versions available.
http://szp-software.virtualave.net/keys_en.html
I use it to remap keypad 1 to [PgDn] and keypad 2 to Shift-F3. I get digest versions of some mailing lists, with about 150 messages combined into one email. To quickly skip through them, I set up Find to look for "X-message" which is part of the header of each message in the digest. But Outlook uses Shift-F3 to do a Find Next, and I hate needing two hands to do that. With the Keys program, I hit keypad 2 to go to the next message header, and if it looks interesting I read it using keypad 1 for page down. Those two keys get me through the whole digest, and I never have to move my hand.