My windows 7 does not complete backups

First what do I mean by " windows restarts the drive " is : that it ejects the drive and then opens it again .
And second I use windows backup

How do you mean "eject an external hard disk" and how do you mean "open an external hard disk"?

Sorry, I don't know Windows backup. It's one of those programs I've never used, although I assume that Microsoft has changed it over the years.
In fact, http://blogs.msdn.com/b/b8/archive/2012/07/10/protecting-user-files-with-file-history.aspx mentions that 95% of the home computer users doesn't use it.

Maybe there's a corrupt file included in the backup? Maybe the disk is full? That's all I can think of.
And maybe it's time to switch to a better backup program.

Kees

Are you backing up to a DVD or CD drive? That's different from an external hard drive. You can eject discs, but can't eject an external hard drive. That's where the confusion comes from, and that's what you haven't clarified yet.
I suggest you get away from the Windows backup program and get yourself a good commercial backup program. I've seen forums fraught with problem reports for the Windows one. I know I was very unimpressed when I tried it. Three I'm familiar with and like are Norton Ghost (which I've been using for 8 years without the 1st problem), Easeus Todo Backup Free, which you can download from http://www.todo-backup.com/products/home/free-backup-software.htm and Memeo which has a 30 day free trial and you can buy it for $29.99 - you can download it from http://memeo.com . You can get Ghost for next to nothing (like I did) if you watch the sales.
The March 2012 issue of PC World was very high on the FREE program from Easeus and so is CNET. In my experience with a variety of configurations I have to say I'm very impressed. Like Ghost it will back up to a networked drive, and it will create a boot CD for when your PC won't boot. See CNET's review of it at
http://download.cnet.com/Easeus-Todo-Backup-Free/3000-2242_4-10964460.html?tag=mncol;1#editorsreview .
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CNET has a lot of backup program reviews at
http://download.cnet.com/windows/backup-software/?tag=contentBody;sideBar .

Some of these are free (last time I checked there were over 300), some have free trials (over 1000), and some are purchase only (over 200).
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External hard drives are best for backup. You can get a 500 GB one for around $60 and a 1 TB one for around $70. You can also buy a 32 GB flash drive for under $15. It's the best insurance you can ever buy!

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I hope this helps. Good luck

if it is internal. They do provide the connector to the motherboard, but you may have to find someone that sells the power connector - I bought both from a computer shop for $10.
The latter is an alternative where you will can use a PATA on How To above. This is that link: http://howto.cnet.com/8301-11310_39-57404939-285/how-to-build-your-own-external-hard-drive/ Darrell