Have you tried this tip?
We run a small network of 5 computers running NT, 2K, and XP. We have had no problems with lagging in the past.
Recently, we moved our office to a new city. Before getting back online, we noticed that when right-clicking on a directory to view its properties, there would be a delay of about 10 seconds. Once we got hooked up with DSL, this delay disappeared. Even though we were trying to access local directories, it was as though Windows (specifically on my 2K system) was timing out trying to see the Internet???
We are now hooked up with a slow 144k DSL, but are having small delays here and there. For example, when trying to view photos across the network with ACDSee, the program is sometimes taking an unusually long time.