"iTunes requires QuickTime 7.5.5 or later"

Hi, I've just bought a 2nd hand macbook. I wiped the HDD and installed OSX 10.5, then run software update until it said there were no more updates. I now have system 10.5.8, iTunes 10.5.2 and quicktime player 7.4.1. Whenever I try to run iTunes I get the above message which then points me at the apple website which then tells me to run software update.

The thing I've done that might have confused things is I organised my apps into folders within the applcations folder. Something I've done since about OS7 but maybe not such a good idea now!

I tried moving iTunes and Quicktime player back into the main Applications folder then running software update again but nothing doing!

any ideas?