I found this in a few different places around the 'net - hopefully it's helpful:

Protect Your Files During a Power Outage

If the power goes out while your computer is on standby, you lose whatever is in memory. If you have any unsaved documents, for example, they're gone. With an uninterruptible power supply (UPS), however, you can prevent data loss during blackouts.

Although the blackout might last longer than the battery run time provided by the UPS, you can prevent loss, even if your computer happens to be on standby and you're away when the power goes out.

• Enable hibernation. (Click Start, click Control Panel, click Performance and Maintenance, and then click Power Options. On the Hibernate tab, select Enable Hibernate Support.
  
• Specify a time for the computer to switch to hibernation. This should be less than the battery run time. (On the Power Schemes tab, set a time for System Hibernate under Running On Batteries.)