I use two iphones, an ipad , andntwo ipod touches on the same computer. They all sync completely and seperately. They all have different names and of course different content.
The solution is simple. I couldnt stand using itunes until i finally picked up the phone and called apple support.
Windows allows you to log in with seperate users. By setting up seperate users on your computer, your i-devices will sync seperately and not recognize or try to sync the other devices.
Not to get too simple, but for example:
Windows user Seans iphone for my iphone
Windows user ipad for the ipad
Log in to the correct user, start itunes, sync up, close itunes.
Then log in as a different user, sync the appropriate device for that user.
Yada yada yada.
Hope this info helps.
BBSean