File sharing fails

Two systems on a network:
Desktop - win xp media edition, SP3
Laptop - win xp home, sp3

Unable to file share. Shares created on both systems. Sharing looking into
laptop from desktop works often. Sharing looking into desktop from laptop
almost never. Browsing network takes a very very long time - several minutes,
and usually fails with "You do not have access bla bla bla". Desktop looking
into laptop takes a very long time and then often works.

Both systems have enabled guest account. Password removed from guest account
on both systems. Both systems have guest account enabled via "Net user guest
yes" command.

both systems have static IP addresses. Both systems can ping each other
reliably. Both systems have HOST file containing address of the other system.

both systems have WINS address in IP advanced config pointing to the DESKTOP.

How can I diagnose this?
Any ideas about what the problem is?

- thanks
ww