Need help with restore operation

My daughter has T 11 and recently had a windows crash (cause still unknown) and could not open windows. She is running Win XP SP3. When all common attempts to resolve problem failed she decided to try a full image restore of a previous backup of the contents of hard drive C. Here are some of the problems encountered:
1. After booting with the Bootable Rescue CD she could not see the Iomega external hard drive that contained the full image backup in the Restore Wizard. She played around and suddenly the Iomega drive appeared - why or how this happened is unclear? Any thoughts on why it did not display at first?

2.The Wizard next asked for a user name and password? Is this normal proceedure? She didn't know which password Acronis wanted? She tried several different ones and her username and password for her Compaq pc finally worked. When she backed up her hard drive she doesn't recall being asked for to enter a username or password? Can soeone explain this requirement?

3. When a full image restore is done on a pc that cannot access windows, does it overwrite the previous contents of the drive that is restored? She is unsure whether she now has two windows operating systems on her C drive (one that failed and one restored from the backup external drive)? Opening My Computer >Drive C > Properties only displays the used and unused contents of the hard drive - no install dates nor does it show two different C drives?

Thanks for any insights - this is her first exposure to the restore function and it underlined our lack of basic knowledge and know-how.

Frank