I think what your asking is if there is a limit to how many times you can restore an image backup (bit by bit bootable image) made of
a Win 7 install using a program like Clonezilla (free) or Acronis True Image (paid).
There is no real limit.
The image itself since it is a bit by bit image contains the activation info that lets MS know that you are activated and that your Win 7 install is genuine.
Where you would have difficulties would be if you restored the image to another identical computer.
The resulting Win 7 install would probably trigger a non activated situation or might not even boot.
This is because another otherwise identical computer would have different serial numbers for the hardware than the original machine had.
The activation data contained in the image would have the serial numbers from the machine that the image was created on.
They wouldn't match the serial numbers of another machine with the same hardware configuration.
This would be like having the same license on two different machines. A no-no.
You can have a separate hard drive with the image restored to it (at least with Clonezilla) that can function as an ultimate backup should your main drive fail.
Since only one drive can booted at a time in the same machine that shouldn't be a license violation.
I'm not sure if this is legal, maybe someone else can verify.
BTW, I make frequent images of my Win 7 (and other OS) installs, at least 2 times a month or more. I also create an image before doing something potentially risky.
For example I created an image just before installing IE 9 beta last week.
Good that I did since I initially had issues with IE 9 and all I had to do was restore my image.
I've restored a bunch of times (at least 50) with no issue.
I use Clonezilla and restoring my image took about 5 minutes.
An image backup is great hedge against disaster.
You simply restore the image and you are back to the point the image was created.
As long as nothing alters or degrades the backup image file, it can be restored as many times as needed.
(to any hard drive attached to the same computer)
That is one very good reason why multiple backups to different media is always a good idea.
I make my quickie backups to the second partition of my main drive and not so quick backups to a second hard drive.
The slowest and most reliable backups are made to DVD. Those are kept in a fireproof vault twenty miles away, so they are impervious to fire, theft or hurricane.
There are several backup programs that work in a similar manner and are reliable. My own choice, going back to 1997, is Ghost. I was using it before Symantec ever bought it from the originators in New Zealand.
I find that I get the greatest flexibility and reliability by running Ghost from a DOS boot disk. Ghost 2003 works great on all OS's up through Windows XP and Ghost 11.5 (the last DOS version of Ghost) works great on Vista and Windows 7.
Having your backup/restore program on your C drive, is worthless, when that drive has crashed or just gone up in smoke. I've run Ghost from a floppy disk (Ghost 2003) and a Flash Drive, a flash memory card and even a CD.
If you are relying on a backup program to save the day for you in case of a HD crash, it's always a good idea to have your Backup/Restore program on multiple media.
MS Backup software? I wouldn't use it at all. Never did and never will.
Not when I've got tried and true Backup software in my hand that's served me faithfully for the past 13 years, through several upgrades.
Where's your emergency boot CD to run the restore if you need it? If your hard drive is destroyed and you want to do a restore to a brand new, unformatted hard drive, you'll need the restore program and your Backup Image file on some other media. Eh?
I agree with oldtimer, Clonezilla is run from a live CD and can restore an image from a flash drive or external HDD.
If the Win 7 tool is used and you have a drive failure you would need to at least install Win 7 on a replacement drive to
use the tool to restore your image.
With Clonezilla or Acronis or another imaging tool that runs from a CD\DVD or Thumb drive you would simply run the
program and restore the image to the new drive.
With Clonezilla that might take 5-10 minutes or so depending on the size of the image.