4 itune libraries are authorized to an old account; my ipad is linked to new account but wont play songs from old account_how to solve?

one very old 1st gen mbp (grampa( must not upgrade past itunes 8 or it doesnt recognize my ipod shuffle. it's running tiger 10.4.11

the macbook from 2009 runs snow leapoard as does the mac mini. they both recognize the new iopd nano and have itunes 10. neither recognizes the old ipod shuffle

all 3 are linked to a dead account, which doesnt even have a password. so i cant buy songs. it just has a death grip on songs i want to share . it was an aol account, which i havent used im years, but it appears in the itunes store.

the ipad 2 is running snow leopard, it is linked to my new mobile me id. when i tried to import songs purchased with the old account, the ipad was not authorized to play them...even though the songs are on hard drives and ipods. AND purchased legally by me -- just under an old account.

also --an extra mac seems to be authorized -- i'm up to my quota of 5 wit the 5th mac not authorized yet! --is there a way to determine which mac is authorized twice?

thank you so much for your help.

ps+last question: my ex left a bunch of song on my music library that i am not authorized to play__ any was to do a quick search for his downloaded music and junk it so doesnt take up space in my library?

thx!