I bought an Asus U36L with no optical drive installed. Can I use UBS external hard drive instead of blank DVD disk and if yes, how?
Can I create a PC recovery disk and save it to an external hard drive rather than burning it to CD or DVD?
I think all you need is a backup file to restore, it does not matter where do you store it.
Any of the above options will allow you to make a system image to an external drive , which is good and recommended. You will however still need a repair or install disk. One way of doing this would be to create the repair disk saving as an iso file to the drive then use YUMI to make a USB repair disk( use the try an unlisted iso option )
you should be able to do that, you will need a backup manager and then choose external hard drive as destination of backup.
Acronis true image
Easus Disk copy