Windows Vista I want to download vista trial :(

Ok basically I want to upgrade to Windows Vista but wont be able to afford it until next month.

Im running XP atm but having serious problems due to a really bad virus I got, and its created great problems so I want to reinstall but have been told I may aswell use vista for this.

I know for certain there are some 30 day trials somewhere but cannot find them.

Can anyone please please help, Getting sick of having to use my rubbish laptop for my main system