Thanks for the reply bitflipper - though to be honest I'm none the wiser for it lol ! My  DAW pc has never been connected to the internet and therefore has never had a windows update in all the years I've had it (I've always stuck to the if ain't broken....... philosophy ) I've tried the installation several times (re-booting between each attempt) with the same result. Nothing else is running and I am the only user and therefore administrator on the pc. I figured that this would be a matter for Izotope, but seeing as how I have come to regard you as the guy who knows everything and is generous enough to share his infinite knowledge with all us plebians I thought it would be worth a go trying here first. I still have an old demo version of Ozone 4 which still works fine, but maybe it's something to do with that, though I would have thought that many people buying 5 will  be upgrading and therefore have 4 installed, so I would be surprised if it was.

Guess I'll have to put it to the Izotope peeps......be a chance to see what their customer support is like before I hand over any cash I suppose. Thanks for your time anyway. BTW on an entirely unrelated note, I put my mp3 on random play the other day and your track (soldier) came on - really enjoyed hearing that again -  I had forgotten what a great tune that was.