Backup Newb

Hi, 1st timer on here looking so any advice/opinions sorry if this maybe is obvious and i waffle on a bit.
So i have a just got seagate expansions 320gb usb external drive doesnt need software for it to work and i have simply drag & dropped my 25gb music and 35gb vids folders onto it , i just click on external drive from "my computer" and everything works fine it all shows up and plays ok.

Question 1
if i now want to save/add more stuff to these "original" folders that are on my PC, and this is important as i don't want have to create new music/vids folders, how do they update on the external drive without having to copy over previous of data already on external drive as obviously i just want to update the extra new music/vids as i get them?

Question 2
I also tried the vista backup for everthing in "My Documents" and it has saved everything as winRars and just numbered them as "backup files" ie 1,2,3,4 etc etc up to 285 so i have go thru winrar process as i have no idea until i open them exactly whats in them, is this normal or i have missed something

thanks in advance for any replies, remember im new at this so no laughing

hello
I can help with question #1, If you try to put the same file in, then a window will pop up warning you that one already exists and will give options on what to do...

choose the option for "no files are to be moved"(something along those lines).

There is also a little box on the bottom of the warning that says " do this for the remaining files", make sure you put a check in that box!!

good luck