What happened to your PGR data absolutely sucks! I appreciate what you are saying about attempting to hack achievements, etc, but the main purpose of this topic is to attempt to hack the PIRS files which in simplest form can be described as a secure zip file for the XBox. These are used for all sorts of things including the Dashboard theme - ideally I would like to hack that so that we can legitimately customise our 360 whilst still being able to use live. In the future when a modchip comes out, we will probably be able to bypass the security associated with the PIRS files, but that would be at the expense of using XBOX LIVE.
The drawback is, a hack like this (and when I say hack, the only way around this would be to obtain the key used to sign the files - which must be somewhere in the 360 hardware as these files have to be resigned as the files are modified) means that the achievements can be modified too. As long as they are modified correctly, there is no danger of getting banned from Live. It would just be as though you obtained them whilst being signed out of Live - when you next connect, they would be associated with your online Gamertag. The good thing is, the file would have to be modified exactly as it would be if you obtained the achievement legitimately, and I'd like to think that is going to be near impossible to do.
Anyway, back to topic. The two ways I can see to getting these files signed properly would be:
1) Obtain the key for signing. This is going to be tricky (perhaps impossible), but MS may have treated this with a low priority as hacking a theme file is not going to leave them out of a pocket a great deal. Unfortunately, sniffing this key out is going to need some advanced equipment and skills.
2) Trick the XBox into resigning the file even though the current signature is not valid. Purely speculation, but there may be a way in which this can be done. It may take a modchip to do it, but once the file is legitimately signed then it can be used without a modchip.