How do I combine identical albums on iTunes?

Itunes says my albums are 300mb how do I make them smaller?

• My ipod set a passcode by itself, it's not the first time it has done it, so i had to reset it to factory default. Then i had to put all the albums on my itunes to transfer to my ipod which used to have around 70 albums. after i reset my ipod and put the cds back on my itunes says that the albums on it are using up almost half a GB so I can only put around 16 albums on my ipod. Can someone please tell me how to resize them Thanks!

• Answer:

  if you feel daring... >_> <_< ... use 7zip and compress files into .7z format mwhahahaha.. XD http://www.7-zip.org/