@ Entwisi: Thanks for the offer of help. Going to do a completely fresh install as I've been tinkering trying to add all sorts of stuff to get it to work... Watch this space...
@ Restless: I'm using "wubi" - it just works. It's a wrapper for Ubuntu linux. You install it as a windows application and tell it how much disk space to use. When you boot up, you have an option to carry on into Windows or use ubuntu for that session instead.
I'm giving it another shot because I'm having such a bad time with Windows 7. None of my programs work any more, so I'm faced with paying to upgrade them just so they will work, or moving over to free, open source alternatives.