Hello
So, you want to rip off Vista? Good intention!
Apparently you don’t know much about OS, so, why don’t you try Linux?
This one for a try- Live CD, nothing to install: http://www.knoppix.org/
Hopefully you will be able to buy XP install cd from your local computer dealer.
There is only one install CD.
When you buy XP install CD, you will receive serial key.
You don’t have to format. Just insert the CD and reboot.
Before you try to install Win XP, get your serial ata driver to a diskette. There is a good chance XP install won’t recognice your serial ata disks wihtout the driver. Hopefully you still have that ancient disk drive in your computer.
If you are in any ways unsure of the procedure, try to get someone who knows to help you.
I think you may need to purchase license of Windows XP in case you want to downgrade your operating system. Consult the company which sold the laptop to you for further information. They may refund Vista or be willing to exchange it for license of XP against a minor compensation.