pausing in Windows 98

I have a dell laptop running Windows 98SE, Office 2000 and PCCillin 2000 that is connected to a Windows NT 4.0 server running exchange 5.5. The machine pauses for about 25 25 seconds every 2.5 minutes consistantly. I have formated and reinstalled everything. Does anyone have any idea what can cause this? It usually has Word and Outlook open.

Thanks
Marc