Won't boot without holding down the OPTION key?

Alright I was going to load Windows on a partition thru Boot Camp. However I decided not to and then used the Boot Camp assistant to remove the Windows partition.

Ever since I got rid of the Windows partition, I've have to hold the OPTION key just to get my MBP to boot even though there is NO other operating system installed on the old partition. If I don't hold the OPTION key it won't boot, it just goes to a black screen.

I'm new to mac's and don't know what to do.

 

That seemed to work for the booting. What about if I'm having all kinds slow down's and spinning balls now?

Something took place while doing this Boot Camp that has made my computer run like a$$.