I bought a 160 GB portable hard drive & backed up all my PC info on it in April.I am now going to travel and want to back up whatever work, files, etc that is on my PC now so that means new stuff from April - present and of course changes to files, etc.

I am a novice and I am want to know will it just add what is new or will it re-copy everything all over again and I will have double of everything.
Thanks

Depends on how you did the back and how you plan on doing it.

This is what I have. I don't remember using any software with it.

Western Digital My Passport Essential 160 GB USB 2.0 Portable Hard Drive WDME1600TN (Midnight Black)

Box Contents - My Passport Essential 160GB Portable USB Hard Drive, USB 2.0 cable, Quick Install guide
160GB Hard Drive Capacity
Installation is a snap because you don't really install this drive; you just plug it in and it's ready to use. There is no CD to install
Powered by the USB bus. No separate power supply is needed
This ultra-portable drive fits easily in your pocket or purse, weighs only a few ounces, and holds tons of valuable data

This doesn't tell me HOW you did your back up. I couldn't find a full description of the drive, but nothing I saw indicates that it does automatic backups. Just plugging the drive in does not do a backup. So you had to do something to backup your internal drive. That's what we need to know.

I did copy and paste
Thanks

Ok, if you did a copy and paste, then do you have the same folder structure on the external? If so, if you do another copy and paste, it will overwrite duplicates, leave any deleted folders and add new ones.

You should use a backup software utility instead. Windows includes one.

Then do you have the same folder structure on the external? Yes I do

Ok thanks Scott!