Despite what others have told you, it is better for your computer (not server) to be shut down every night. Windows 95 and 98 particularly likes to be restarted. Windows 2000 and XP are better designed to be on all the time, however, your system may still heat up and reduce the life of your hard drive if you leave it on all the time.
Set you office applications to autosave and automatically save a backup copy, these are disabled by default.
Keep your operating system and critical applications up to date.
If you use Outlook Express see this page for useful information..how to reduce spam, recover lost messages and more