Macbook Pro Running Slow: Spinning Ball of Death

Question

Hello, all
I decided to go ahead and make an account here because I have looked in various different threads for a solution to my problem, tried various different things, and nothing works so far.
Basically, my MBP is running super slow as of the past few days. Every few seconds, the spinning ball of death appears, all typing stops, reappears again a few seconds later, and my browser feels like I'm running on a dial-up connection. Any application feels like that, really, on- or offline.
I've done a reset of my SMC. I've run Disk Utility and repaired the disk. I've run OnyX. I've tried looking for abnormal tasks taking up a lot of computer usage in the Task Manager.
Is there anything else I should be trying to do? I'm really running out of options and am quite frustrated with this whole situation, about to throw my laptop out the window.
I updated recently to OS X Mavericks, but that was after the problem had started. The problem persists in 10.8 and 10.9.

Answer 1

Is this a Standard MBP, one with the built in Optical (DVD) drive, or a Retina model?
You could try reinstalling a fresh (NEW) copy of OS X on an external drive and run the system from that external to test. If the system runs smooth, although slower than from the internal drive, with no beachballs then you have some type of problem with the internal drive. What that problem is could be the drive is failing or it is to filled up with files or the cable going from the drive to the logic board is failing.