I experienced the same thing months back with Vista x64, and originally thought it to be a hardware failure, because the 0x124 stop error usually occured after some intense disk activity.
And this is going to sound like a really odd solution, but it worked for me, and if your BIOS has settings to do so, it may very well work for you too.
Turn on your computer and go into the BIOS. Then find the entries pertaining to your hard disk controllers (IDE and SATA), then if a settings is available to change, make sure that "32-bit Disk Access" is turned on for all controller ports.
Like I said, and odd solution, but it worked, as you can see from the post I made in August 2007 on the Vista Forums: Solution to STOP 0x00000124