Practice computer safety 1st:
1) Use a surge protector on your system, a battery back-up is even better! Don't forget to protect your phone line (get a unit that has in and out jacks for your phone line). Make sure everything is properly grounded and if possible run your system on its own circuit.
2) If it's important back it up! If it's really, really, really important backup that backup! This can be as simple as making copies, of important data, to floppy/zip disk or alternating tapes used for backups, CD-ROM's or other media. If your unsure what a backup is - stop everything and learn! Just get a backup routine, keep it simple and stick with it!
3) Get and install an anti-virus program that provides regular updates. I prefer Norton Anti-Virus
4) Keep all your paperwork and original software in one box and label it. When you really need it you will now know where it is! - You should keep your original boxes for at least one month. It's always nice to have the original boxes if you have to ship the unit back to the factory for repair.
5) Keep extra printer supplies on hand. It seems you always run out after the stores are closed! As a general rule, do not plug Laser printers into the same surge protector as your computer.