Maintenance check

Here's one for the admins out there: I've got about 70 users in a mostly outbound call center as part of a larger domain model. What I need is some suggestions on a checklist for routine (and maybe not-so-routine) maintenance to keep these babies upand running. They run pretty well, but I've been tasked to develop a SOP for this and would like the input of other admins as a double-check of sorts to make sure I didn't overlook anything. These machines are Dell and Compaq only. We're running Nt4 SP5, Office 98, and running Outlook 98 as the email client. Personal folders are allowed, however surfing (currently) is not. Oh yeah, we use roaming profiles, too. Thanks for the help!!