With such a large base wouldn't you sic your IT team on this and why wouldn't they just have Microsoft on the line helping you out.
Somethings fishy about your claim.
But slow mapping is a well known issue. Rather than me duplicate articles like http://www.google.com/search?hl=en&source=hp&q=xp+slow+network+browsing you should tell the forum that you already did that.
I have a very special problem and Im not sure it should go here.. anyway here is my problem.
We manage about 4000 pc ( in win xp and win2k) in about a 1000 stores around the country. In some of theses store we are experiencing some very strange mapping behavior, from the office to the store, the completion of a drive map is about 1 minute. in these store we have a vpn built on a cable conection, in store the protocol is affected by this issue because the ping and the regular tcp/ip connection are very good , even the map, when its finaly establish, is working properly and can sustain some big transfert at a regular transfert rate. What is making this an issue is that our credit/debit system is using a UDP protocol to initialize its connection to the server and this slows downs the debit/credit transaction to a lingering 2 to 3 minutes.
This is what we see on with ethereal when we are trying to map :
"session setup andx request ntlmssp_negotiate"
we see 5 or 6 time dis message with 7 to 9 sec wait time in between.
I looked up all theses symptome on the net and on multiple forum and still havnt find a solution.
I am listenning to any possible option .
Thanks and have a nice day