Unable to access Help - Photoshop CS

For some strange reason I can't access Help from within Photoshop.

My browser opens with :-

http://%1%20"file:///D:/Program%20Files/Adobe/Photoshop%20CS/Help/help.html"

but it can't find the page.

If I simply put :-

D:\Program Files\Adobe\Photoshop CS\Help\help.html

then it can.

I've re-installed twice (painful) and still get the problem. I've searched the registry for the link but can't find it.

Any suggestions woulkd be appreciated. Btw what does %20 mean?

Thanks

%20 is how web browsers interpret spaces when online.