It only takes four easy steps to install another system software on the hard disk of your PS3. Yeah, you heard us right! Not only can you swap 2.5" SATA HDD, you can change the operating system (OS) software. Of course, you need compatible third-party software: but we're still waiting for more details on that (www.playstation.com just says "details will be posted soon").
But, just so you know, here's how you'd do it: