I have a cheap PC and iTunes isn't deleting songs off my iPod for me...

I realized I maxed out the capacity of my little nano and proceeded to delete old songs to make way (about 30 songs, I just clicked and deleted)- they no longer exist, but my iPod has no more space, according to iTunes...my nano is installed on a bargain basement PC, so I hope that there can be a resolution to this....HELP! =~(~~~~puddle