Cannot restore from Partition

Hi there; trying to restore windows 8.1 from a backup partition. When I insert the repair disk, go to repair/troubleshoot/advanced and select the backup image, it tells me that it needs to backup the entire disk. That is strange. When I created the imagebackup, I had two partitions: C:, with the O.S., and E: as a backup. Is there no way around it? I have started copying the image to a usb drive, but it would really take a LONG time (about 300 GB), and I am wondering if the recovery function will find it. Thanks in advance for helping.