[Solved] Convert external drive to internal or sell and replace???

Hi everyone,
I purchased a WD MyBook 1TB external drive about a month ago, because it was on sale for about $60.00 after a coupon. I've been using it mainly for playing/storing HD movies (mostly 720p stuff, but a few 1080p as well) and for music, as I stream them through a wireless music bridge. While HD movies play without any hiccups, I've read that this drive isn't the best for that. Anyway, I've concluded the drive is a PITA, as there's no power switch, it's limited to USB, etc. The drive is a WD10EAVS, which I realize only has 8mb cache and is the lowest of the lowest when it comes to green drives and I've even read it's really Sata-I and not Sata-II.
I've recently built a new pc, which I plan to have powered on all the time, so that I can access the music wirelessly and watch movies. I currently run the OS's on a WD Blue drive and I'm wondering if you think I'd be better off selling the external for 50-60 dollars and replacing it with something better or just using my current drive internally. I don't even mind if I wind up losing a few bucks to replace it, but I feel like it might take a while to sell a 1TB external in Pittsburgh lol.

I've also read that if I pull the drive out of the enclosure, I can actually register the drive's serial number with WD, thus giving me a 3 year warranty as opposed to the lousy 1 year that comes with the external. Anyone know if this is true?

Thanks in advance