Update all hardware-related drivers
: video, sound, RAID (if any), NIC... anything that interacts with a piece of hardware. It is good practice to run the latest drivers anyway. 4)
Update the motherboard BIOS according to the manufacturer's instructions. Their website should provide detailed instructions as to the brand and model-specific procedure. 5)
Rarely, bugs in the OS may cause "false positive" 0x124 events where the hardware wasn't complaining but Windows thought otherwise (because of the bug). At the time of writing, Windows 7 is not known to suffer from any such defects, but it is nevertheless important to always keep Windows itself updated. 6)
Attempt to (stress) test those hardware components which can be put through their paces artificially. The most obvious examples are the RAM and HDD(s). For the RAM, use the in-built memory diagnostics (run MDSCHED) or the 3rd-party memtest86 utility to run many hours worth of testing. For hard drives, check whether CHKDSK /R finds any problems on the drive(s), notably "bad sectors". Unreliable RAM, in particular, is deadly as far as software is concerned, and anything other than a 100% clear memory test result is cause for concern. Unfortunately, even a 100% clear result from the diagnostics utilities does not guarantee that the RAM is free from defects - only that none were encountered during the test passes. 7)
As the last of the non-invasive troubleshooting steps, perform a "vanilla" reinstallation of Windows: just the OS itself without any additional applications, games, utilities, updates, or new drivers - NOTHING AT ALL that is not sourced from the Windows 7 disc.
Should that fail to mitigate the 0x124 problem, jump to the next steps. Otherwise, if you run the "vanilla" installation long enough to convince yourself that not a single 0x124 crash has occurred, start installing updates and applications slowly, always pausing between successive additions long enough to get a feel for whether the machine is still free from 0x124 crashes. Should the crashing resume, obviously the very last software addition(s) may be somehow linked to the root cause.