Convert from Vista to XP

Hello,
My Sony Laptop got a Virus, my tech tried to repair it but in the process he lost my XP version and now the Sony has gone back to Vista version, and now he is UNABLE to put into it the XP version, can you help me with this problem?

When I purchased the SONY last year model no:VGN-FZ38GU this model is a Vista model but Sony managed to set it up in such manner that they loaded XP for me and said that in case in future I wanted to use Vista I just have to press F10 and go to Vista.

Now my Tech, has messed up the whole machine and he cannot load the XP version on this machine!

I would really appreciate your input on the above matter.

Thanks
Redgs
Shainaz