Why will hard Drive to SSD not allow for startup?

I recently took my entire Macbook pro early 2008 completely apart to see how everything ran and decided that I wanted to upgrade a couple of things. So far, I upgraded the ram which does work, however I upgraded the original hard drive on the computer to a 2.5'“ Sata 6 Gb/s SSD which hasn’t gone over very well. I transferred over all my files cloning the original drive and putting it onto the SSD, but during startup I get the prohibitory sign. I’m assuming that means there’s a boot issue. How do I solve this?