I have an iPhone and 2 non apple computers with iTunes. I want 2 Apple IDs on my phone and the content off 1 computer backed up on another.
Thank you for posting today. I'm sure we can find a workable solution for you today.

Apple allows multiple computers to hold and play content, sync to devices, and all of that via iTunes. For you to play the content from the older computer on the newer one, here is what you will have to do:


Copy over the content from the iTunes Media folder on Computer A (old computer) to the iTunes Media on Computer B (new computer). Typically, the iTunes Media folder is located under C:\Users{your user}\My Music\iTunes\iTunes Media. (See special note on Step 2)
Import the music and all other files to your newer iTunes library. The easiest way to do this, if you want all content, is simply to place all of the files when copying them over into the "Add to iTunes" folder located within the iTunes Media folder.
When the item is in the new iTunes on Computer B, try playing one of the files. You will be prompted to authorize your computer for your dad's account.
Sign-in to your Dad's iTunes account to authorize. This can be done on up to 5 computers, including the original, and can be modified at a later time via iTunes Store -> My Account -> Authorized Devices
You should now be able to sync as needed with your iDevice and others


Please note that if you had apps under the older account and sync those to your phone, if they need to be updated it will require the other login (though this is about to be phased out). Music, however, should load without issue as long as the computer that you synced with retains authorization to play. The iPhone won't care which AppleID bought it, as long as it is able to make it onto the device (either by purchase on the iPhone or by purchase/authorization/etc on the computer and synced up).

Hope this helps!