Quote: "I have an Intel Core i5 2500 processor, I believe it has Intel HD Graphics, right?"
As n008 pointed out,
latest CPU cores have in-built a HD Intel Graphics GPU.
Best way to know for sure if you got the required hardware is to try to run the Intel® Graphics Checker (as stated in step one:
http://dc145.4shared.com/download/5iJ_AKv-/iGCheckerSetupENU_2_1.msi) if it doesn't complain after the hardware checking, then it works
Quote: "it seems impossible to activate the Intel HD Graphics with a discrete GPU already installed"
Yeah, well you could turn off the GPU card in the bios, connect the monitor to the motherboard output, install the intel drivers... I don't really recommend you to mess around just for this, but thanks, I appreciate it all along.
Quote: "The checker won't install for me. It looks like it gets to the end then instead of giving me the option to close the install it looks like I only have the choice to cancel. (My best guess, it wassn't in english)"
My fault

, I updated the link with the english version, so at least you can tell what's hapenning:
http://dc145.4shared.com/download/5iJ_AKv-/iGCheckerSetupENU_2_1.msi
According to intel this should run for:
Platforms: Intel® Core™ i3/i5/i7processor with Intel® HD Graphics (desktop/mobile). Microsoft* DirectX* 9 or 10 Application Programming Interface (API)
Operating Systems: Windows* XP Professional SP3 (32-bit), Windows Vista* Ultimate SP2 (32-bit) or Windows 7 Ultimate (32-bit and 64-bit)
Thanks to all, please let me know if anyone finally gets the report, I would pay for it as stated before
Oh and it is ok if anyone wants to grab the mpl3d discount code that appears in the first post, that's what it is for