Yeah But point proven. I had the same Notebook using the required drivers, which by the way (not theorically!! =) ) were working great for me, even for some games like WOW.
I think you don't understand yet this... dell has not customized any dell 1525 series, because of their model. dell 1525 uses again a GM965 chipset, there's "no customization" involved in that chipset. And any intel chipset using a GM9XX uses their own northbridge/southbridge/IGP because of their arquitecture. Low cost, low energy usage, etc. The BIOS must be delivered by Dell by any means because of the custom vrambios inside the main bios.
What you're saying can be applicable to 60% laptops with custom hardware built. IE: Newer Intel with ATI GPU chipsets (My brother has one.. and I can happily stick a report giving in great detail its specs), but not some chipsets made by intel, like in this case, because those chipsets involve the whole pack (IGP/NB/SB/IOController/CPU) into a single codename.
Why I posted those drivers above? Because the Intel X3100 GMA965 was designed by intel. And the mainboard chipset embedded is the GMA965.
Just to clarify anyway, everyday we learn something new...