Mate, I am absolutely gutted for you. I've been doing a cookbook and would be devestated too if it went down the spout. I really hope it shows up.
You screwed up installed XP Malc. You shouldn't have done anything other than getting a new drive, installing OS and treating the old as storage. Why you went for XP when you had 7 I don't get? I'd still do that if I were you. A new drive is peanuts... All the "professionals" will do is basically this as a first step. It'll take then 10 minutes.
The repair disc was supposed to be w7, i put it in and selected repair when it was nearly done i realised it was xp not w7 - too late it had overwritten w7 ?