Several weeks ago, I bought Windows 7 and Parallels Desktop 5 for Mac.
My intention was to install Windows 7 on my Mac-mini using Parallels Desktop 5, but the response of the machine became so slow that I un-installed them.
I suppose that the size of the memory of my Mac-mini, that is, two gigabites was not enough to use Windows 7 as a guest OS on my machine, which has a Snow Leopard OS. Then, I found VirtualBox and installed Windows XP and 7 on my Mac-mini. They are working well, and VirtualBox is free. My XP machine revived as a virtual machine in my Mac.
I installed Windows XP on my Mac mini mainly because I have a lot of files made by Ichitaro(一太郎), word-processing software for the Japanese language. I am very accustomed to its interface and “かな漢字変化システム” that is called ATOK.