Win 2K/XP Pro slow network browsing

Windows 2000 & XP Pro browse the network dramatically slower than our older win98 machines. I have XP machines with P4’s and 256MB of RAM that browse network mapped drives slower than P2’s with 128MB of RAM but have Win98. Could this be something to do with WINS or DNS?

We are running Small Business Server 4.5 (Which is basically NT 4.0 with a BackOffice license to run SQL and Exchange). We are not running DNS locally and the DHCP scope is not providing any DNS settings to the clients (only WINS). Our server points to our ISP’s DNS server for resolution. I just wonder if it is Win2K/XP’s preference for DNS over WINS that is causing the slow down. Thanks.