Curious but what would be a recommended OS/Boot loader on ThinkPads where you want to keep the original OS installed by Lenovo and adding an extra hard drive instead of the DVD. To be able to have the Service partition working together with ThinkVantage button you're not able to make any changes to the mbr.
Suggestions?
The way I'd like to see this solved is by something like AirBoot, which replaces the mbr, but with the addition of supporting the ThinkVantage button. (How hard could that be? it's just a button...)
The service partition can easily be started from any boot manager, even the OS/2 one.
I usually uses AirBoot and it's my preferred boot loader; but then again; I could actually live without the working ThinkVantage button. Actually there is diskette image available from Lenovo to recover the original ThinkVantage button feature to work as out of the box. Guess that the next best solution would be to have an OS selector installed on the primary first partition using for example Acronics (to mention one of many) OS selector.
GRUB is pretty powerfull and has options to do a lot of things. It is also well documented with source code. I suspect it could be made to be used with the ThinkPad button ...