i wouldn't be the one to ask, as i switched to GNU/Linux mainly because i hated everything Microsoft did after Windows 2000.
Just using XP and Vista to test if my applications/websites still work.
Vista has many drawbacks when it comes to speed. I even noticed that people brought back their PC's due to Vista destroying their hard drives.
Would be bad to destroy your rig
Setting up VirtualBox is pretty easy and done within a hour.
Switching later on would be hard though, you need to move your whole virtual drive content to a solid drive partition, then run the Vista DVD again to modify the MBR.
Another issue is that Vista needs a lot of power so you can't get all benefits of Vista through a VM.
However, moving your dual-boot to single boot is not easy as well. You can't just move your second HD to be primary "C:" because it will be missing the windows "boot" files.
Upgrading XP to Vista is also hard, there might be software conflicts.
Just dual-boot and when you're done with XP just do the following:
- move important files to some sort of backup device
- Format C: and D:
- Swap you new fast drive to be primary
- Install Vista fresh
- Restore backup data