Microsoft Small Business Community Blog : Do I have Downgrade Rights for my software that comes in Action Pack?:
If you have used an XP license from your Action pack, that license now has a time limit on it… it’s valid only up untill the time you renew.
If you are still running on OEM versions of XP, you are fine and do not need to upgrade to Vista. You can stay on your OEM XP.
To all of those who I urged on Action pack without realizing this limitation, my personal apology. I had no idea that the license terms would be like this. When my action pack renews in April, I cannot upgrade XPs to Vista as all of my line of business applications don’t work on Vista. Fortunately for me the Action pack for my firm (MPAN) is a recent change and I didn’t rely too much (one machine) on that Action pack media. So I’m going to be retiring that machine in April to be compliant.