There's one thing about Windows Vista and Windows 7 which really sucks: unlike Windows XP, it cannot boot from an external USB hard disk.
To make things worse, running Vista or Windows 7 inside VMware also isn't such a great idea if you're planning on doing development. As soon as you're running some huge application like Visual Studio and then try to open something else in the background, it's starting to get really slow. It's not only CPU power, the external USD hard disk is also much slower than an internal one. I first experienced the problem by accident when I had Windows Update configured to automatically download and install updates in the background - and turning that off still didn't satisfy me.
Yesterday, I finally considered the external hard disk a failed experiment and called a local Lenovo shop to get the real problem fixed and replace the internal hard disk by a bigger model; I'll get it replaced on Tuesday.
Since I don't want to spend too much time reinstalling everything again, I'll move my entire Linux installation onto an empty partition on that external disk. Linux doesn't have any problems booting from such devices, so this move should go rather smoothly. Next weekend, I'll migrate everything back - I Google'd a bit, and it seems to be possible to migrate a Windows installation to another hard disk without reinstalling, so hopefully this'll save me a lot of time.