Is this the Cognito you mean, grizly, or are you talking about the mobile messaging Cognito which takes over the entire device?
Messaging Cognito I can tell you a bit about - With the Siemens SX-56, the software installed itself from an MMC card. If you took out the MMC card and performed a hard reset it would go into normal Windows Mobile. However, you do lose ALL your messages. I've stopped working with Cognito units now so I couldn't tell you what they did with the XDA2 - though it's a safe bet it's in the Extended ROM. Unfortunately the software is pretty watertight. Early versions had bugs which would cause the phone tones to be heard when you hit the right regions of the screen - and, I think, allowed dialing! - but they probably fixed that (not that there was actually any way into the OS from the phone) so you're pretty much stuffed unless you overwrite the ROM. And then you won't have the Cognito software or data, and you'll be totally screwed.
Wenn du geflamet worden bist, dann weil du es verdient hast.