Mac OS X v10.5 and itunes 10.7

Yes, that is correct.

First check to see if your Mac can run Snow Leopard:

Requirements for OS X 10.6 'Snow Leopard'

http://support.apple.com/kb/SP575

Whilst Apple have withdrawn Snow Leopard from download, you can still get it from Apple by calling 1-800-MY-APPLE (if you are in the USA) and they will supply the SL DVD for $30. You can also purchase the code to use to download Lion from the same number.

If you are outside the US call your national Apple Helpline:

http://support.apple.com/kb/HE57

If you're in the UK, use this number: 0871 508 4400

When you have installed it, run Software Update to download and install the latest updates for Snow Leopard.

i dont really understand what your saying. my mac wont allow me to download it aswell (i am trying to do it as an apple advisor said to do this as lots of my purchased songs didnt download). it is very frustrating because it downloads and then after half an hour and its done downloading it says "do you want to install itunes" then i click on that and it say "im sorry but itunes acnnot be installed on this computer". i alresdy have the old version of itunes.

You need to be running Snow Leopard 10.6.8 in order to use iTunes 10.7. You are running leopard.

Now follow the instructions in my post.