Windows XP host hangs on guest install

I have a problem during the installation of an Ubuntu guest OS onto an WXP host (Toshiba Satellite Centrino Duo with 1GB ram). The virtual environment makes a certain amount of progress with the installation. About halfway through my whole system hangs, with the fan (and presumably also the CPU) going flat out. I have to power off my laptop and restart it to recover. I have the same behavior from Ubuntu 7.10, 6.06 and 5.10. Oddly when I used a Windows 2000 instalation disk I had lying around, I also got a similar result with the system hanging about halfway through the install.
I have virtualization enabled and the result is the same with both 256 and 512Mb ram allocated, I also used the alternate CD from Ubuntu with no difference.
Can anyone give me any help on diagnosing my problem?