Help... my macbook pro is super slow now!

Okay... so yesterday my macbook was fine. It started up quickly and everything worked well. This morning ,however, I woke up and turned it on (or attempted to) and it didn't start until 5 - 10 minutes later! How could it have slowed down over night?!

Here's some information that may/may not be helpful:
Last night I put in a DVD and I took it out this morning. I also changed the area settings for the quicktime player so that the DVD could work. I didn't do anything else... Mehh helpp =_= please.

Is it making a clicking sound? Have you tried restarting to see if it still takes that long? Do apps take a long time to open? I'm thinking your harddrive might be dying/dead...