iPXE and SCCM 2012 Task Sequence

[SCCMDrivesmeNuts]

I'm in the midst of trying to figure out how I can stage WindowsPE to the local HD to kick off a task sequence rather than using software center in Windows. We noticed a paltry 50% success when trying to launch the TS this way from Windows XP.

We've had the most success tricking SCCM into thinking we're PXE booting, but have noticed that it eventually figured it out before launching the TS. My google searches led me to iPXE, where a number of people have claimed to get this working using iPXE and I'm wondering if someone can provide me with the following registry key so I can validate this myself.

HKLM\System\CurrentControlSet\Control

I know SSCM uses this to initially determine how the system was booted, but does eventually try and validate this after the fact. Any help is appreciated. Thanks