There is no way in hell I'd install ubuntu with the unity desktop on a windows xp machine with 1Gb memory. You didn't specify the cpu ... it may be single core ... but even if it was a dual core, no way. I installed unity on my 4Gb i3 laptop and it was too slow for me.
On my netbook, which has a dual core atom and 1Gb, I've never considered installing unity but I've used the other 3 ubuntu desktops plus mint with the Mate desktop. Mate was actually rather slow and Mint tech support is as bad as ubuntu's is good. I wouldn't recommend mint for linux novices, period.
KDE (kubuntu) actually isn't bad in a 1Gb space (especially considering it's considered bloated) if you tweak it for speed. But it still has a bit lof latency. Faster than the windows 7 starter that the netbook came with though. KDE is endlessly configurable, which I like but many wouldn't, and it's usually done through GUI tools rather than editing config files. Which is nice.
XFCE (xubuntu) is pretty fast and light, and it works well in 1Gb. But I didn't find it balzingly fast, and it doesn't have the features of KDE. Which means I have to do a number of things by running separate apps, which slows me down.
LXDE is really fast and light. Really fast. I'm running Lubuntu 13.10 on my netbook now. It's the only one I've tried that has such a major speed difference. But there are a lot of configuration things that you can't do from a GUI, which means editing config files. Not so easy for a novice.
But I'm finding lubuntu a little clunky, the support doesn't seem to be as good as with other ubuntu desktops, the development seems stagnant from what I've read, and I have to wonder why lubuntu installs the XFCE power manager.
I may keep using lubuntu ... I'm willing to forgive some rough edges for this kind of speed. But I may upgrade the netbook RAM to 2Gb when the 14.04 lts comes out in a couplle of months and reinstall kubuntu.
Don't install multiple desktops. That can introduce hard to diagnose problems. Better to just download and burn the iso's for different desktops and try them in live mode.
If you install lubuntu ... which is probably a good idea on an old 1Gb machine, don't install 12.04. Unlike other versions, it wasn't a long term support version. Lubuntu 14.04 is going to be their first lts. I'd wait for that, though you could install 13.10 and upgrade later.
LXDE (and XFCE to a lesser extent) do not have the eye candy. I've seen lots of forum entries by people who add things to try to put eye candy into lxde. They seem to have all kinds of problems, and it won' be a small and light desktop anymore. The reason the newer flashy looking desktops don't work properly on old hardware is mostly because of the eye candy. These desktops like unity and cinnamon require 3D hardware accel just by themselves.