Servers
Check System, Application and Security event logs
Check free hard disk space
Check fan speed and server temperature
Check RAID Array / Hard Drive Management systems (verify fault-tolerance status)
Install appropriate Patches and Service Packs
Check that Virus definitions are current
Run a full virus scan of local hard disks
Check Virus scan logs
Review/remove quarantined files
Check that any scheduled tasks are completing successfully
Review recycle bin & delete temporary files
Review file system permissions

Backup Systems
Check that the correct tape is mounted
Review backup activity logs
Check the backup catalog
Ensure tapes are being rotated off-site
Check that backup media is in the correct media pool
Clean tape drive heads
Periodically perform test restore from prior backup and verify integrity of the restored files
Update offline backup after any significant system change (or every three months)

Uninterruptible Power Supply (UPS)
Perform UPS test and check configuration
Check battery life

Off-site Backup Server (if in place)
Review synchronisation logs

E-mail and Internet
Check Postmaster mail box & review/delete undeliverable e-mails
Check queues on the mail server
Check firewall logs
Review Internet data downloads (by user if applicable)
Check and test Internet access restrictions

Workstations
Check free hard disk space
Check that Virus definitions are current
Run a full virus scan of local hard disks
Review/remove quarantined files
Check Virus scan logs
Check System, Application and Security event logs
Install appropriate Patches and Service Packs
Review recycle bin & delete temporary files
Visit all users and resolve any problems

Network
Check DNS database consistency and name resolution
Check WINS database consistency and name resolution
Check DHCP database consistency
Check Hubs / Switches for high utilisation / collisions