Running CS3 from External Hard drive

I just backed up my mac to and external hard drive, including all my applications and CS3.

I don't have the installation discs for CS3 so my question is:
If somehow CS3 was to get erased from my mac would I still be able to run it (photoshop, illustrator, etc.) off of the external hard drive?

I didn't "install" it onto the drive only backed up my whole computer to it, hence my question.

Thanks