W2K WS needs reboots every 4 hours

We have an odd situation here with a W2K laptop being used as a workstation. Seems it takes as long as 5 minutes to connect to it’s mapped drives when it boots up, then it slowly bogs down and after about 4 hours it is responding to all apps so slowly that it has to be rebooted. I don’t know if the mapped drives and the slowing down are related. The laptop is a fairly new machine, bought last year, has 768K of ram. It generally runs MS Word, Excel, Lotus Notes, MAS200 all day long. Any ideas onwhere to look for possible problems?