slow network response??

[reboot1678]

We had an existing network using seven 98 workstations and one NT 4 server. Swapped out the NT server and replaced it with Windows 2000 server. Windows 98 is still the platform on the seven other workstations. The new server has 768mb of memory, onboard LAN card and running Promise Raid controller to mirror drives. I'm using Active Directory in Windows 2000, using DNS and DHCP and have installed service pack 3. DHCP is assigning IP addresses to the workstations. I also deleted the D6277990-4C6A-11CG18D87-00AA0060F5BF registry key in Windows 2000 that can be a cause of some slowdowns. The PCs are networked with a HP procurve 224M switch.
If I ping a computer from the server, the response is very quick. If I go through network places on the server to see the computers on the network, and click on one of the computers, the response time is good too. Also if I ping the server from the workstation, that response time is good. The workstations are using a data program that resides on the server. When executing the program from the server itself, the program runs quickly. But accessing the program from any of the workstations is significantly slower some larger reports take 5 minutes or more to come up. Not sure why I have good ping times but poor program response. Is there some authentication issue not resolved? I am not sure what is causing the slow down....any ideas?
Thanks!!