Do I need to download and install quicktime with 10.5

I have just spent alot of time uninstalling I Tunes 10.5 and then re-installing it. Every time I tried to use I Tunes would not open. I then found two old Quick Time program files lurking in the Windows System 32\Wow folders. When I deleted them I Tunes worked perfectly. Therefore it looks like you no longer need Quick Time for the latest version of I Tunes to work. I have opened my list of programs and Quick Time no longer appears anywhere on my system!

Hope this helps.

Is it necessary to install quicktime with the 10.5 version of iTunes?

You might still need it in order to play some older media files. See the following document:

iTunes 10.5 for Windows: Older media files may require QuickTime

... but otherwise you should be fine without the QuickTime Player application on the system.