There is a discussion in atul's Carsoft thread
about using Carsoft with Vista. If you haven't read it, I'll save you the suspense: it doesn't work. (I thought about adding this to that thread, but didn't really want to hijack it.)
For those of you that don't know, Windows 7 was built on the Vista kernel, so it's generally true that if something worked in Vista it will work in Windows 7 and anything that wouldn't run natively in Vista has problems in Windows 7 as well.
As they developed Windows 7, Micro$oft worked on improving XP mode (and the other compatibility tools) and they are indeed much better. However, while you can use compatibility to start installing WIS (at least the XP version) in Windows 7, the installation will not complete and you won't be able to run it. (I tried.)
The business, professional, enterprise and ultimate flavors of Windows 7, however, come with a license to run a virtual version of XP (this is 32-bit, regardless of the host Windows 7 platform). Out of curiosity, I decided to try and load my old copy of WIS in that virtual environment and it installed and runs fine. However, I didn't try to install Carsoft for one very basic reason: it requires a hardware interface to do any good. For basic PC hardware, such as drives, mice, monitors and (most) printers, Virtual XP in Windows 7 works fine. However, for quirky stuff it won't...and we already know how quirky Carsoft is. Moreover, Carsoft really needs to be on a laptop and better one with a serial port, and anything that old isn't going to run win7 business, professional, enterprise or ultimate...so why bother?
I have an old XP laptop that runs carsoft and my old WIS just fine, and if you're going to use either, that's my suggestion. Get an older laptop with the serial port, replace the hard drive (a weak spot) and just load XP, WIS and/or Carsoft. Snag-it if you want good screen captures, and that's it. Keep it off the internet and you won't need any patches, updates or anti-virus software. That's my suggestion, to just treat it as a dedicated tool, and use it that way.
Hope that helps a few of you out there.
Side note: If you are running Vista, it's worth it to upgrade to Windows 7 unless you simply need a new machine. I've upgraded several Vista PCs and laptops to Windows 7, and in each case they have run better and more stably than with Vista, and for laptops the power management is a little better, too.