No boot device found

So, I tried to install XP through Boot Camp but for some reason couldn't get it to work. Since I didn't really need XP anyway, I just went into OS X and deleted the Boot Camp partition. But now, every time I turn my Macbook on, I have to hold the option key and select the (lone) Macintosh HD partition or I would get a "no boot device found" error. Now, it's not such a big problem since I could still use OS X, but I'm pretty sure that's not how it's supposed to work. Does anyone know how I can fix this?

 

Thanks! I had a feeling that was it but never bothered to check. Now I feel like an idiot lol.