This is an interesting topic because locking mobile phones, handheld consoles, etc is really annoying and just a way for the retailer to "force" you to keep to their network/service (i.e. you can't sell it later to other people unless they want the same provider).
I have a similar problem involving my Navini wireless modem, which is locked to one of Unwired (an ISP in Australia) re-sellers called Exetel (also an ISP in Australia).
Basically, Exetel have locked the modem to their network and I am no longer with them. Now I have this modem that can only be used on their network, whereas other Unwired re-sellers don't do this.
What's really funny is; Exetel offered to buy it back from me for $30 (when I paid $150+ initially). I didn't agree with that offer and a month later they called "out of the blue" and offered $35. Another month later they offered $45..
<rant> I own the equipment and will hack it to bits before they get their hands on it! :D </rant>
So if anyone knows of Navini "hacks" out there, be sure to let me know.