Can I put songs onto my iPod without erasing all my current songs?

My brother's moved his PC out of our dads house because we're renovating, as we need more room (stepmother = bun in the oven) YAY!

Anyway: Once upon a time, I loaded all my songs onto my iPod from his PC which is now at my mums house except he doesn't have it connected. I really want to put songs onto my iPod except I cannot… because if I connect my iPod to a whole new iTunes, all the current songs will be deleted because it's a new system or something.

Basically, I'm looking for an alternate way to load songs onto my iPod using a different iTunes on a different PC without all the other songs on the iPod being deleted as the new songs are added.

Is there a way around this? I've been told there is!

I would LOVE all the help in the world. Don't respond saying just get your brother's old PC hooked up again (he's deleted everything on it).

Thanks!
-Tim :]
One time I added tunes onto my iPod from another iTunes and all of the all-ready-there songs were gone.
One time I added tunes onto my iPod from iTunes on my friend's PC and all of the all-ready-there songs on my iPod were gone after the sync.