I chased this one for a long time and found this to be a solution;
XP slow network read-data xfer.doc
Problem: XP takes a long time to show any files or folders when looking at certain network drives. This can occur with Explorer , Word and other programs. In one case, when an XP machine was looking at a folder on another XP machine (which had many folders and thousands of files), and the user was in Word, trying to open a file; each time a file was opened, a 36 second wait occurred before any files were displayed.
Cause: The interframe gap of Ethernet packets is too short on certain network adapters. This is supposedly a hardware problem and not specific to XP or Microsoft. A Microsoft article (315237) says that it is Intel Etherexpress 100B network cards (I found it a problem with an Intel Pro/100 VE also). I suspect it may show up in a lot of 100mb Intel cards.
has registry fixes
but;
I went to the network card setup/advanced section and changed the following to fix the problem;
Interframe space was 1, now 20
Adaptive Tuning was low end now middle of slider
Retransmit Interframe Spacing was 10 now 15
Now, from within Word, file listings of network drives list in a second instead of 36.
This fix may not allow the card to work as fast as it should, but it is massively better.
gr