The 7800go, 7900GS go, and 7900GTX go are all incompatible with the D810, M70, I9300, and XPS M170/Gen2, because they were made for the newer Core Duo series Dell laptops. Note that the 7800GTX go IS compatible because was designed for the M170 series notebook. The real problem behind why the cards will not work can be either one of three things:
1. The cards electrical specification has changed since the previous generation. So the pins on the connector to the motherboard are still the same physical connector, but different pins carry different signals on the new versions.
2. The older laptops system bios is not recognizing (and therefore refusing) the newer cards. It might be possible to hack the bios but a person would need a testbed of the different cards and laptops, along with bios programming expertise to be able to get a working solution. I tend to think this is no the problem though, because for all intents and purposes, the M70 bios is unlocked, and will accept even the 7800gtx without flashing. Yet it still will not accept the 7900gs as others have experimented with.
3. The LCD backlight inverter on the older laptops draw more power than the newer laptops. This would mean that the newer cards could not provide a suitable output voltage to the older displays, requiring the newer display to be swapped along with the newer cards. This line of reasoning fits in with the research in the other M170 thread, where it was found that a M1710 worked with the 7800GTX, but the 7900GTX would not work in a M170.