Yeah, funny how you can feel snubbed by not getting alerts. Just as long as it isn't a friend trying to get ahold of you for something important.

So I held my breath and installed your download. The DSDT seems to start up fine if a bit slow. Lots of additional temperature sensors in iStat widget AND the CPU is running (or reading) a lot cooler with the MacPro 5,1 ID. I also reset the BIOS to the settings in your video (Not sure of the C State enabled and then setting to C6. I always thought that was for non-Core Intel CPUs). Also, I have an MSI GTS-250 1GB GDDR5 so no worries about ATI kexts. I DO have a couple of IDE drives installed but don't really need for OS X as they have an old install of XP Pro but I haven't got all the data files moved to my Win 7 drive. Sound finally works without resorting to running Voodoo kexts but wish the new sound setup didn't give off a loud pop over my speakers when loading. I'll move the other unnecessary kexts out of the /Extra/Extensions folder and see how that goes next.

I still have the hard reboot problem - in both OS X AND Win 7 so I want to think it's BIOS related. I've been unemployed for a while otherwise I'd go and get a new PSU to try and see if that's the issue. The installed Rosewill PSU works great other than having that one bugaboo.

Thanks again for your help. I still don't have the faintest idea how to edit a DSDT but grateful that yours seems to do the trick without any tweaks.