What specific songs are you talking about?
If you meet these requirements on your computer (XP and above for a PC)
With iTunes 10.3 or later and iOS 4.3.3 or later, you can download your previous purchases directly to an iPhone, iPad, iPod touch, Apple TV or computer that has beenassociated to your Apple ID.
Then you can redownload iTunes purchases by:
If your XP computer has has iTunes 10.3 (which is supported) or later and your country supports redownloads then you can redownload iTunes purchases by:
To see if your country supports redownloads see:
Then you can sync to your iPod