As seen in Microsoft's links here and here, this is potentially useful, but also potentially dangerous tweak to use.
So this is more of a hardware question (I know they say Pentium 4 multiprocessor systems), but I've seen mentions of XMM instructions in Athlons too. Some places say XMM is SSE, some it's SSE2...
The question is - how do I determine if THESE XMMI they mention are present in my processor? Everest and CpuZ don't mention XMM, I don't know if it means they are absent or the programs don't check. I've downloaded cpuinfo.de which promised to show, but seeing it incorectly recognized my CPU as Pentium 3, I'm very suspicious.
Specific processors I ask about are Athlon XP (Barton) 2600 and Celeron 2.6 Northwood (in a laptop, but without fancy features), but it would be useful to know about more types.
This registry entry is present in Windows Server 2003 (and I suspect in other Microsoft OSs too).
GL