Yes, it is called a Uninterpretable Power Supply (UPS).
They vary from units that basically give you a minute or so up to several hours of run time. The basic ones are around $40. They are good for areas that have poor power with lots of surges and brown outs. The usually do not have software and hardware that allows the computer to shut itself off automatically.
Better ones have a USB plug that plugs into your computer and software (or Windows own settings) on what to do when the power goes out (shutdown, standby, hibernate, how long to run etc). They start around $60 for one that will last 5-10 minutes, up to several hundred for ones that last for over an hour.APC
makes some good ones for a decent price (as well as a few other makers).
My sister has some "dirty" power at her house. Her computer kept crashing and her HDD died. When I replaced the HDD, I added an APC UPS. It has software that tracks the UPS usage. Within 4 weeks she had over 30 instances where the UPS kicked in due to power problems (but she said the power never went out at the house).
I have 4 in my house. 1 on my sig rig, 1 on my HTPC, 1 on my server and 1 for my router and modem (I have Vonage, so this keeps my phone working in a power outage). Only the one on my server has a USB plug for the Computer and is set to shut down automatically once battery reserves get down to around 5 minutes (according to teh software, that gives me around 25 minutes of usage with the 450w UPS).Edited by blupupher - 5/27/11 at 12:15pm