This is not a new tip, it was already gave by many others, but it worth mentioning again. When you want to try beta software the best solution is using a virtual machine, to avoid the installer to break your dev machine. With windows7 you have another option, the xp mode.
AS you can see I can launch visual studio 2010 from my main machine, but it runs inside a virtual pc virtual machine. This is fantastic because you do not have to worry about anything, just launch it and it runs like it was installed on your sistem, except from little details, like the windows bar.
When you launch VS2010 you can see that it runs inside virtual machin
But this process is transparent, once the VM is started, Virtual pc ask me for credentials and now I can run my VS2010 beta2 without the risk of breaking anything.