WIN XPsp2 - WIN 98se wireless network file sharing impossible

Hi,
I have two PCs (WIN 98 SE and a WIN XP SP2) and a laptop (W2000) linked to a
wireless network with a D-link DI 524 router. Internet connection was never a
problem, but it took a long time enabling file and printer sharing, probably
because of the different WIN OS. (W 98SE PC too old to upgrade.)
I had temporary success following advice found here (thanks Micha and
Holzman!); eg, NetBIOS over TCP/IP, etc. but, now, I get "workgroup not
accessible. You may not have permission..." message on both PC. The only
changes I can think of was installing SP 2 on my XP computer, but I made sure
that file and printer sharing is enabled in the firewall exceptions, without
result.
(I also tried to implement static DHCP on my router to get fixed IP for
security reason, but went back to dynamic after developping internet
connections problems.Don't think it's related though.)
I also tried starting over from scratch using XP Wizard (mistake?) but got
an "unable to complete" message when using XP CD (as instructed) on my
WIN98se PC.
Thanks