Thanks for the reply Fireberd.
I finally solved the problem this evening. Like all problems it is easy when you know how. It is a separate mic.
I used the 64bit audio driver 64bit_Vista_Win7_Win8_R270 from realtek, I used the UK1 version. You have to be patient initially you think nothing is happening, then it takes over 20 minutes to download.
Run the C270 exe file, restart, then control panel, sound, and the mic (el al) is there. Then properties, change to microphone, adjust volume (initially set to zero), restart again and it works. You may need to adjust volume in user programs like Skype.
I spent hours on this problem, one has to ask, does it need to be this difficult. What made it difficult for me was the HP website saying for 64bit pro you dont need to download a driver at all. Once past that the solution is clear, find the right driver(s). Fooled the company that refurbished it too, they didn't have a clue