Question about Back Up

First of all, hello to everyone visiting this forum!
Second, I couldn't really find a good place to post this thread, so I hope it's in the right section of the forum.

Now, my problem is that I want to create a back up, using windows 7's back up options. I've read some tutorials on this site and other sites, and it's really simple. The only problem I'm facing is that I want to select my External Hard Drive (1TB), but I can't find if it will erase this hard drive first? or will create a new folder? I've already created a system image, which creates a new folder on my hard drive, so I can restore from that. But I also want windows to automatically back up my modified or created files once every week. Will windows create a new folder so that the files that are already stored on my HD will remain?

My second question is, if I decide to let windows back up my Documents and Settings folder every sunday for example, and during the week I delete some files. Windows will notice on sunday that some files have changed or have been deleted, will it also delete them from my external HD because they aren't on my HD anymore? I suppose not right?

After creating a system image, it prompts asking to create a system repair disk. If you have an original windows 7 cd, this is completely unnecessary right? (If yes, why does windows offer this function? Everyone's using windows 7 is supposed to have an original disk right?)

Thanks in advance,
Crimson

Skip that last question, windows probably supports this function because there are many pc suppliers which give you a PC running an OS without supplying you with a CD.

Hmm, I did some further reading, and I think that windows 7 backup is not doing what I want it to do.
I want it to copy files modified on my pc to my external hd. Windows backup doesn't really copy the files, but writes it in its own format which can only be opened with the windows back up utility.

What I want is that if I have created a text file called D:/Schoolstuff.homework.txt and ripped a movie D:/Movies/The Dark Knight.mkv), I want those file to be automatically copied on my HD as follows:
E:/Schoolstuff/homework.txt,
E:/Movies/The Dark Knight.mkv,
so that I can open them on any computer.

I'm basically just looking for a utility that clones selective files/folders. Does windows 7 have a function like this? or are there any other application you suggest?

Awesome thanks,
Any other programs that can do things like this? Ideally I want a program that detects when my external hard drive is plugged in, and then starts backing up files. But I can imagine that such requirements are a little bit too specific.

Thanks for your answer.

PS. the questions from my first post still remain out of curiosity.

Do a google search for synchronize folders or a similar term. Microsoft has one or two free programs to do this.

A couple are

Karen's powertools
Syncback
Second Copy
Synchromagic
GFI backup

And undoubtedly others

Win7 does incremental backup to your choice of location. It does not format the drive as long as it is pre-formatted which yours should be if it is storing other files.

Test your Win7 Backup image by booting from WIn 7 DVD (not everyone has one for many reasons, like buying a Win7 computer) repair console "Recover Using An Image" to see if it autodetects the image and proceeds to reimage. Just don't click the final Next unless you want to reimage to point when you backup was.

The image backup is to save you from ever having to reinstall Win7. It can also be incrementally backed up, but I do it manually monthly.

Thanks for the replies!