Core Multiplexing Technology must be enabled when you want the system working in multicore environment. As is known 45nm Core Microarchitecture based processors, such as Intel Core 2 Duo E7500, is not officially support by Intel G965 chipsets, and working under 1066MT/s FSB, this chipset puts much higher requirements towards the physical memory modules.
Why it goes to blue screen, when enabled the CMT?
I am not so sure it is the hardware or compatibility problem! But you might possibly run a second O/S, such as Ubuntu, put it onto a USB stick. And boot your machine with CMT enabled with that USB stick, to check what your computer would go on. If perfectly with the second core working well, you might possibly reinstall Windows. Or, there might exist compatibly problem, and it is a hard problem, could not solved by software or patches onto its firmware.
Before Core 2 released, there was only Pentium Extreme processors equipped with 1066MT/s FSB, and it is a power hunger monster!
The above processor might be the extreme potential power exploiter.