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.
Cheers Mates!
Old Timer