Yeah Stally, I reckon you're right. I see that the top version of Win 7 has a compatibility mode, but I'm bloody cautious about parting with more money without being confident that it'd work.
I'd been thinking that having a Windows machine in the house would let me use the programme version of NAIPS (which I much prefer to the web version). So it's really just the disappointment that things didn't work out - it didn't seem like a particularly demanding expectation at the time !
Might have to splash some coin on one of the commercial flight planning programmes ... Time to hit the search function and see what people like !!