The majority of new computer systems and notebooks are currently being shipped with Windows Vista. Unfortunately this is causing huge problems for alot of users. Vista still has plenty of driver problems and software incompatibilities. So for those that have gone out and purchased a new computer, they are experiencing nothing but problems, whereas their old Windows XP was working fine. Its just a shame those great new notebook deals don't ship with XP.
The good news is that you can downgrade to Windows XP, without having to actually purchase a license of XP. Microsoft have provided a downgrade option but it does take a bit of work.
Firstly, you need to have a copy of Windows XP media. Any copy will be fine, even if it has already been activated. After installing the copy of Windows XP, you need to call Microsoft and activate it with your non-activated Vista license key.
You will still need to re-install XP and wipe the current installation of Vista. Here is a quick guide to get you started:
You can find more useful information here: Windows Vista downgrade
Good Luck!