Replying to Ipod question

Ok so i have an ipod and here is an example...
I put 100 songs on my ipod...after i delete those 100 songs off my comp to save memory, then i download or import 1 new song which i really want on my ipod...so i plug in my ipod and when it updates that one song...the other 100 songs are deleted off my ipod because i deleted them off my harddrive.
This sort of thing has happend


So my question is can i delete music off my hard drive and the next time i go to update my music will it stay on my ipod somehow wwith out being erased???
word



L-MOB fo lyfe