I also have an old Belkin 5D6020 (Ver 1) and a NoWiresNeeded PCMCIA card which fit my iPAQ sleeve.
Under PPC2002 at least one of these cards would connect to my home network (802.11b) after downloading some drivers from Compaq site onto the iPAQ. I use a Compaq sleeve with a PCMCIA card slot.
Since the PPC2003 upgrade I cannot get the cards to function. I am unable to find suitable drivers on the web. The message I get when inserting the cards is "Unrecognized Card, Enter the name of the device driver."
I have tried varations of PRSIMNDS.DLL - picked up from browsing other sites but am not confident I have copied the right drivers across nor that they will work with these cards and PPC 2003