I've seen this question (and its converse) asked in several places on the web but with either short unsatisfactory answers or no answer at all. I'm interested so I ask it again:
My 2-yr cell phone service contract with Sprint is finally about to expire and I'd like to leave Sprint and switch to a pre-paid Virgin Mobile plan instead (Virgin piggy backs on the Sprint network anyway and Sprint doesn't offer pre-paid itself). That's all fine and good, but I'd prefer to just keep the the cell phone I currently use for Sprint and use it with VM when I switch. It's a perfectly good phone and I have no interest in buying another (ya know, reuse, rather than recycle and all).
I've heard that software on phones can be "cracked" or "unlocked" or something so they can be used on competing networks. You'd think a Sprint to VM phone move would be particularly doable.

So is this possible?