itunes on pc has different apple i and password than on my newly purchased ipad, so I cannot sync my purchase tunes to my ipad because the pc version of itunes will not accept the new ipad id and password or my old ones.How can I change pc to ipd id

I had itunes on my pc with a apple id and password. I recently bought an I pad and set it up with another apple id and password because i gave my old Ipad to my wife which used the old apple Id and password. I wanted to start fresh on the new ipad. My wife subsequently changed the apple id and password on the old ipad.

Now, when I tried to sync my past itunes purchases to my new Ipad, the pc will not accpet the new id and password. So how can I get my pc id and password to agree with my ipad id and password. I do not want to change my apple id and password on my new ipad for fear that I will mess up all my aps, podcasts, etc. not to mention various other settings I do not know about ( the unknown unknowns, as Rumsfeld might say.) Or can I sync the old ipad (hers now) with mine.?

Basically, I hope someone has a helpful, but simple answer.