I just bought a new hard drive because my old one is full…Is there a way to use my old copy of Vista on my new hard drive (and throw away the old hard drive) or am I going to have to get a whole new Vista per Hard drive?

I have Windows 7 Professional installed on both my laptop and desktop. The graphics on my desktop look a lot different and nicer than the graphics on my laptop. I don’t understand why. They’re both the same 32-bit operating system.

Can someone explain?

Our computer was fried in an electrical storm. Fortunately I have a backup of our files and settings on an external hard drive (this was made using Windows XP Professional). All I really care about is restoring our files to a different computer. My choices are: using my husband’s work computer, which also runs Windows XP Pro or use our soon-coming new computer which will have Windows Vista Home Premium.
Is it possible to open the .bkp file in our external hard drive using my husband’s computer and restoring just the files (I don’t want to overwrite his work stuff)? Or will everything be restored? Is it possible to do this on our new computer with Vista, even though the backup was made using XP?
Help!
To clarify:
When I made the backup, I used XP’s backup utility and selected “Files and settings.”

I have a laptop that came with Vista and an old desktop with XP. If I were to downgrade my laptop from Vista to XP, could I use the XP product code that came with my desktop?