GOT IT!!!
I installed Activdriver4, turned off the User Access Control (both as suggested) and tried again following the Promethean install help guide that came with the download.
No luck! I kept getting a Windows request for instructions on what program to use to open the files (these are the as3a files, the ones the install help tells you to open 2nd).
After tearing out some more hair (I'm not the crispest cookie in the box) I figured that A) the install help guide probably didn't apply and B) something was missing. On looking at my download file I noticed that there was not just ONE setup file (the one referred to by the install help) but FOUR. Figuring I had nothing to lose I opened and ran them all... and Hey Presto! Thereafter the other files opened and installed like a dream, the ActivStudio icon appeared on my desktop and my Good Lady opened it up and it worked!
Fingers crossed... accepting that Promethean won't offer support and doesn't acknowledge this, Yes, you CAN run ActivStudio on VISTA!
Note: Not sure if installing Activedriver4 was needed, after all, I have no Active board connected and this laptop will only be used for creating flipcharts at home. Also not sure if turning off the User Access Control was needed.... Must remember to turn it on again!
P.S. Wife now thinks I'm wonderful.