BSOD during or right after Windows 7 clean install

Dear members,

this is about PCs consisting of: Asus P9X79 PRO, BIOS 4607, Intel i7-3930k, Samsung SSD 830 (system/software), Samsung H204UI (data), AMD FirePro V4900, Windows 7 Professional 64bit

The PCs have been self-built in 2011 and ran simulation software nearly 24/7 until April 2013, after which they were not needed and switched off, mains disconnected. After switching two of them back on in November 2013, Windows 7 updated - and soon a BSOD-fest ensued, even in safe mode, no dump files could be written, no software could be installed to monitor or check things, only the event viewer filled up by the minute, so I switched the PCs back off.

Instead of unskilled tinkering, I decided to update their BIOS, which worked, and then rather install Windows 7 anew, formatting the SSD in the process. Now, just before the installation finishes, each PCs freezes with "The system encountered an uncorrectable hardware error." and "STOP: 0x00000124 ...".

How should one go about this? I am absolutely clueless. Has the processor gone bad on each machine in their eight months sleep? No hardware has been added/removed, I opened the case and checked if something became loose, the PC have not been moved, shaken or kicked, the environment is dust-filtered.

Thanks for any hint!