Well, I unchecked it - and on shutdown I got a full blue screen warning about doing it - and on restart I got the "Windows has recovered from a serious error" message. The machine seemed to work fine, but it wasn't happy. And I didn't want to risk not having it reboot (part of the shutdown warning was that it might not boot up again!) so I re-checked it when it did boot up. The error log showed this: Error code 10000050, parameter1 ba691000, parameter2 00000001, parameter3 8053a593, parameter4 00000000. After I re-checked it and rebooted the original error was all I saw.