by pooing -_-
upload them
When the songs were erased from your Ipod, you can never get it back, maybe you have plugged in your iPod to other PC/laptop that has itunes. You should connect your iPod only to the PC where you have installed your own itunes.
You can do it on iTunes from your PC
if you mean like you bought songs on your iPod and they were never on your PC than plug your iPod in, hit sync, and it should ask if you would like to transfer the items on you iPod to your computer so hit transfer
download itunes onto that PC and upload the photos onto itunes and then you can download the photos onto your iPod.
open itunes and sync
Plug your ipod touch into itunes and click sync.
Depending on what format your songs are in, it should most likely be able to transfer onto your iPod.
getsharepod Njoy Also google TouchCopy
Well, if you're using an actual iPod, I'm afraid you're already out of luck, iTunes does not allow you to sych songs from your iPod to your iTunes library or Computer, only vice versa, this is a feature iTunes does not allow to prevent pirating of illegal downloaded music.
Forever, until you get rid of them that is. You can do this on itunes on your PC or, if you've got an iPod touch, you can delete them on there.