Floydy, not trying to get at you in any way, promise, but I think I should give an 'official' view here!
Kitz.co.uk does not recommend that users install pre-release software on their main computer, as it could make your system unstable. There is also no guarantee against a bug in the beta software causing data loss, although this is (thankfully) a rare occurrence.
We would especially recommend staying away from anything to do with the base operating system on your computer, such as major operating system changes like service packs, until they are officially released.
If you do like trying stuff before it's released, then if possible, use a spare PC, or virtualisation software like VMWare or Virtual PC. That way, you won't risk your main, day-to-day PC.