this should help
link
http://www.ntu.edu.sg/CITS/getting+h...cketpc2003.htm
otherwise just google for something like
setting up wifi for pocketpc
or
connect to wifi with ppc
most likely you have to change the networks option for WORK/THE INTERNET
change it all of them to WORK
thats what does it for me.
also have you got any other device to work from that router...just to be sure that the problem is not on the other side.