It is still possible to buy computers with XP, but not for much longer. if you want to put XP on this laptop you will have to sacrifice the Vista licence and purchase a full retail copy of, I assume, XP Pro.
As for trying to get on with Vista, of course you should, its miles better than XP, and it networks like a dream. I don't understand how you can think its user unfriendly. Give it a chance, and buy a good book on how to use it. You won't regret it. I don't see how losing files can be anything to do with Vista, sorry.
Office 2003 will work with Vista without any problem, I have this setup on two machines, and its a bit cheaper than 2007, so go for that if it suits you better. It will still read the files created in 2007 with the aid of an add-on. Make sure you get rid of 2007 first though.