i found the problem. nothing to do with the amount of memory, as i expected. if windows needed more than 1GB of memory to run simple tasks i would worry more than i already do about why people chose it.
Anyway. for some reason there was no installer at the path windows support told me that the installer should be at. i was getting error 1719.
so i downloaded the installer, but ironically, it wouldn't install. anyway, i then discovered from fluke that service pack two wasn't/hadn't installed properly (by fluke the latest .net frame work wouldn't install and i was looking through my windows update install history and saw it didn't install).
Anyway, i installed this, and with it came the windows installer. i then tried again, and got a new error, (can't remember what it was but it was fixed very simply), but then got 1719 again.
Anyway, found an article, and the directories are very different for the 64 installer, but there's only one support page for it. if i had read the whole page properly first time round it might have helped.
Anyway, turns out windows had installed the 64bit installer in the registry as the 32bit one, so the image path was wrong. change that and it works fine, and in-fact better than xp. I've now got to reinstall the ones that kinda installed in the hope they'll run better