Here you can download Windows 7 RC: http://technet.microsoft.com/de-de/evalcenter/dd353205.aspx and you need a Windows-Live-ID account, also you have to be fast because the download is only possible until 20th august 2009.
I wouldn't install Windows 7 RC on your normal desktop PC, but the VirtualBox is a good possibility to test Windows 7. Who doesn't know what VirtualBox is, has to read my next post, which follows in 2 or 3 days.
The installation is very simple and also rookies shouldn't have any problems with the installation.
The firewall gives a big variety of adjustments. These adjustments would be nice on my XP-comptuer.
The embeded service center does his job well and the annoying bug reports. which we know from Windows Vista are gone now.
I installed different kinds of applications and you can say that they work well under Windows 7 and you haven't these silly unreproducible crashes.
So now, you can test Windows 7 until 2010 for free. Who wants to use Windows 7 after this date has to pay for the Update.
I'll continue with testing Windows 7 and I'll post Bugs and other useful infos about Windows 7!