Can't install older version of iTunes

[Redspice]

My son was putting tunes on a friends iPod & it said we needed to update iTunes. So he did, but I didn’t find out till hours later. We had a screaming match. Anyway I deleted the new iTunes & tried downloading version 10. It gets to the last stage of installing, then it says “Rolling back action.” Then, “The installer encountered errors before iTunes could be configured. Errors occurred during installation. Your system has not been modified.”
How do I get version 10 to completely install?

 

[eob2000]

You need to fully uninstall everything related to apple from your PC (iTunes, Quicktime and any apple services (Mobile Driver, Bonjour etc)

Also why do you need version 10. Any Apple devices will work in the latest version of iTunes