I have a Gateway 600YGR laptop. It's 4 years old and thus out of
warranty. My battery shows a full charge when I take it out of the bay
and press its button, but my system (Windows XP SP2) says the battery
has 0% power left. I ordered a brand-new battery from Gateway, which
had the same problem, so I returned it and I assume it's a problem
with the notebook.  At this time, a new notebook is not in my budget.

I almost never take the laptop anywhere, but on occasion the power
plug is jostled and comes loose, and my laptop dies. I just want
protection from this happening. At Best Buy I was told there is such a
thing as a spare battery that plugs in via a USB port. Unfortunately,
the only model they had was not compatible with my computer.  I also
know very little about uninterruptable power supplies.

To summarize, which would be least-expensive for protecting my laptop
when the plug is accidentally bumped - a UPS or a USB battery? Please
address compatibility with my laptop (e.g. a brand and/or model name
or number), and a general price range.

Caveat: 1. Although the 600YGR, when I bought it, was supposed to have
USB 2.0 ports, they seem to be 1.1. I don't know how to confirm this,
but when I plug things like my iPod and my thumb drive in, I get a
message that they could run faster if plugged into a higher-speed USB
port. I have 2 ports and the message occurs in both. I add this info
just in case a USB battery needs a 2.0 port to work.

The idea of pumping power into a laptop via the USB strikes me as very odd
- they are supposed to send /out/ a small amount of power.

A UPS is an Uninteruptable Power Supply, basically a load of lead acid
batteries that take over if the mains supply ceases, they also tend to
clean out current spikes.

I don't think you really want one of those either.

The simplest solution would be to get a hot glue gun (they are used in
assembly for fixing things into place, also in flower arranging) and
glue the plug into the socket.

As an embelishment you could get an inline plug and socket and cut
your charger cable - sure your laptop will have a short 'tail', but
that should not be much of a problem.

ups is no good. all that will do is make sure the cable still has
power in a power cut. you can pump power into a usb port but I would
avoid it besides which it would cost almost as much as a 2nd hand
laptop.

Firstly the usb 2 thing could be your driver. Get a usb2 driver and
install it and see if it still happens.
http://support.gateway.com/support/drivers/dlcenter.asp

secondly rather than a glue gun that will make it hard to remove I
suggest a nice big strip of gaffer/duck/masking tape. that will make
it much easier to remove while still secure.

Really? The USB battery thing at Best Buy was only $150, same as a new
battery from Gateway. (As I said before, it wasn't listed as
compatible with my laptop.)

I hadn't thought about the UPS only ensuring the cable has power -
d'oh! Thank you both.  I guess I'll try the duct tape route.