darco, I think you're doing it wrong. You should be using something relatively stable, Jaunty, as the host for the unstable virtual virus-trap.
My preference is to use Felicia, which is rock solid and stable, as the host platform for both of them.
I agree with you that Win7 doesn't show off very nicely in a VM. I've had it in Virtualbox since it came out, and side-by-side with XP it is the loser every time. The only thing that Win7, in a virtual session, does better than XP is launch programs. Boots to login slower, loads the desktop slower, is otherwise overall a pig compared to XP, but IE7 launches faster. I can go from cold start to Excel document open in half the time by launching XP. By my estimation, none of the "improvements" to Win7 are realized in a virtual session because I'm not giving that pig full direct access to my hardware.
Jaunty-alpha, on the other hand, plays very nice in a virtual session. Nice enough that I entrusted a bootable partition to it and have been relatively pleased with it. But it is too much of a hassle for me to be expected to reboot to play with something, so 99% of the time I just boot to Felicia. I've tweaked my Felicia to boot faster, but Jaunty beats it. Jaunty is faster still. I look forward to putting Jaunty on my Dell netbook.