ISScript error help!!!

I am trying to download the iTunes 7 installer including Quick Time and I keep getting this error on my computer. I have searched the internet trying to fix this problem and have tried several things and it does not work. I am tired and have been working hours on this problem. Please help me. Thank you so much!!! OH! I do have Quick Time on my computer too. But I guess it is not the right version. I don't know.

First error:

"1: The InstallScript engine on this machine is older than the version required to run this setup. If available, please install the latest version of ISScript.msi, or contact your support personnel for further assistance."

I click ok then I get this second error message

The installation of Quick Time did not complete successfully. iTunes requires Quick Time.