You can run Vista under VMWare (or any other virtualizer/emulator) under Linux, OSX, or anywhere else without violating the Microsoft license. You just can't do so with the cheaper Home Edition. The real drive behind this is actually OSX. A lot of people are starting to use OSX as their main system and falling back to Windows only when they need to do something with windows-specific software. Since such a user rarely spends even 25% of their time inside the Windows guest OS, a lot of people were buying the cut-down Home Edition and saving a ton of money by not paying for all the features the were never going to use. But MS had been counting on widespread adoption of the higher tiers of Vista. So, to fix *some* of the hemorrhaging "future revenue", they changed their EULA for Windows to prevent using any of the basic-tier OS products with virtualization.
Besides (and to get back on topic), there are currently no such constraints on XP, and for ham soundcard software not written to understand the new Vista sound layer, XP makes for a more reliable (and *vastly* lower overhead) execution platform.
