Totally agree with
writhziden about VirtualBox. It's a great system. There are some software packages that require VMWare Fusion such as Flight Simulators, etc. but most software will run just fine and never know they are not on a native Windows installation.
BTW: Not sure about Windows 7 or Windows 8, but for Windows XP, it's best to have about 512-768 MB RAM or the system loads slowly on my Mac (which only has 2GB RAM maxed out). Just something to think about. You might not experience that with Windows 7 or 8. Not sure. But play with settings to optimize it for your scenario.
There is another side to why another, totally unrelated OS should be used as a host; particularly if you are using Windows as Guest OS(es).
With Linux as noted no registry to hook into but it can't run .exe files anyway. There are totally different types of executables between these two OSes.
I would suggest taking a look at VirtualBox again. I use it in Linux (running a Guest OS Windows XP) and on a Mac (also running a Guest OS Windows XP Pro).
VirtualBox works very well with most Guest OSes, but if you are using Windows, I would suggest using a Linux or Mac Host, or at the VERY LEAST, not using ANY of the interaction between the two oses, such as shares, etc., if you are using a Windows Host. Just in case. I have no worries sharing folders/files/clipboard between Linux or Mac Hosts and Windows Guest OSes. I am very careful regardless though.
If you must use a Windows Host as well as a Windows Guest, STRONGLY suggest totally isolating the Guest from the Host if you are trying to test malware on the Guest OS (this is something I would never do BTW). See my Sig quote for my reasoning about that.
And yes, very nice snapshot capabilities with VirtualBox.
Hope that makes sense.