HP laptop won't boot after CPU upgrade Celeron 420 to T2050 Dual Core

[Mechmaniac]

So, I have this my friend's aunt old HP 530 laptop that is damn slow.
Since I have many wrecks in my depot, I found a socket compatibile CPU for it and try to upgrade the old Celeron 420 1.6/1M//533 with a Dual Core T2050 1.6/2M/533.
I updated the BIOS and changed the CPU and restarted the laptop with no problems.
In the BIOS the new CPU was correctly recognized and the "Dual Core CPU support" parameter present in BIOS setup auto-switched to "Enable".
I saved and restarted, but after POST (I see HP first screen) the system didn't booted up and remains stucked with black screen with no blinking lines.
I tried switching useless parameters in BIOS setup, but did'nt resolve.
I put back the old CPU and Windows started up normally after HP screen.
Shut down again and replaced CPU with T2050, tried to change the "Dual Core CPU support" parameter to "Disable", and the damn Windows started up normally.
The CPU was correctly recognized, but in task manager I see only 1 thread, so I have a single cored T2050 working.

Anyone knows the way to make it work correctly in Dual Core mode ?
This HP BIOS is very Cryptical...

 

[popatim]

I'm afraid that your notebook only has the Mobile Intel 940GME Express Chipset, which can only run Celeron processors. In order to run a Pentium C2D processor, your notebook needs to have the Mobile Intel 945GME Express Chipset.

 

[Mechmaniac]

The chipset is 940GML (Intel SL825) ad it should support other Dual Core CPUs...

I read for example in this discussion:

I have a asus a8h here that has the 940gml chipset. It came with core duo T2050 @1.6ghz 533fsb 2mb cache and i upgrade to core 2 duo t5500 @1.66ghz. 667fsb 2mb cache. I run 2 gig ram. 1 card is pc2-4300 (266fsb) and the other is pc2-5300 (333mhz) both run at the slower speed. The extra ram and and 5400rpm 500gb hard drive greatly improved performance. for day to day use.

 

[Mechmaniac]

The chipset in an Intel SL8Z5 (940GML) + SL8YB.
I've found this list:
http://www.cpu-upgrade.com/mb-Intel_%28chipsets%29/940GML_Express.html
But I've also found other conflicting opinions / experiences...