The problem was that no sound was picked up from my microphone when I tried to record a voice-over to a video track. This was a problem in both PowerDirector and WaveEditor. Strangely there was no problem with other voice apps like Skype. I'd had a clean install of PD and WE. The Win 7 machine had recently had a clean bare metal install of Win 7 64 bit.
After some searching around on the web I visited the site of the motherboard manufacturer (Foxconn) and downloaded their latest 64bit drivers (they were described as Vista64). Checking on my PC I discovered that Windows 7 had installed some generic 32 bit drivers for the sound chip embedded in the motherboard.
I located the install program in the zip file downloaded from Foxconn and installed their screen drivers - just a couple of clicks really.
Problem solved. This may not be the solution for everyone with a similar problem, but it may be an avenue of research for them. Charles Smith
Twitter: oaksys