Found this link while pursing Pocket PC Thoughts.
WEP Strong Key Generator version 2.1 by Warewolf Labs and Kraix.com Basically, this web page lets you generate either a random WEP key in 64, 128, 152, and 256 key lengths, or generate one based on a given custom key.
I know I had some problem a while back getting a new key inserted into my lap top so that it would work with my new key I created for the access point. I wrote a small vb program to convert the ASCII to HEX. This site takes it one step further and generates the ASCII text to begin with.