Hang/freeze on Nero,Google earth install

Euskadi

Hi all,
My PC hangs when I try to install for example google earth or NERO.
I am running WIN7 and everything else works fine and I'm quite happy with it in general.
when I install google earth 5.2 for example it does everything to the point of extracting the files from the package,the green bar on installing goes up little by little,reaches the end and then hangs.The window is still open but it is doing a green version of KITTS red light(Knight rider,Hope you understand what I mean!!) for hours and hours,ARGHHHHH.
With nero it does the extracting files thing and when they have been extracted disappears,END OF STORY,without installing anything.
It smells like a virus to me but countless panda scans and win defender scans say the pc is clean as a whistle.WHATS WRONG????????
Any ideas,what can I do?

Thanks for listening.

mp22

is uac on or off,in other words might there be a window open behind nero setup waiting for a input?