Ok. I've read a few things on this issue.
It seems Toshiba stores model information in the DMI strings in the BIOS. When you boot up with the Restore CD's the first thing it does is look for this string in the bios. This is normally referred to as a "BIOS Locked CD".
According to Toshiba there are 2 possible fixes. One would be to try updating to the newest Bios for your laptop. It is supposed to update the DMI on its own. Whether it will or not I'm not sure as I don't have a P105 to try this on.
The other thing you may be able to use is the 'Toshiba Notebook PC DMI Update Utility' (http://cdgenp01.csd.toshiba.com/content/support/downloads/toshdmi10.exe
This will allow you to create a CD to boot from and pick your model and it will do the rest. Hopefully the P105 is in the list for this DMI tool from Toshiba.
Hope this helps,