Last night, I took the hard drives out of an older MacBook and a newer MacBook, and swapped them, which shouldn't be an issue because both are Intel based and everything is compatible. After swapping and turning both Macs on, the older Mac with the hard drive from the newer Mac works perfectly fine, like it should, but the newer Mac with the older drive is having issues. Everything works great, except when I try to play any sort of media. Songs will not play in Preview, iTunes, Safari, or anywhere else. The same occurs with video, freezing to the point where I get the infamous "spinning wheel of death."
Everything was working perfectly fine right before I swapped. I've eliminated RAM possibly being an issue and I don't think it's the video card, as I was able to Preview and iPhoto through RAW photos from a 5DmkII.
So that being said, does anyone have any suggestions?