"PCIe 2.0 is not completely backward compatible with PCIe v1.x. Graphic cards and motherboards designed for v2.0 will be able to work with v1.1 and vice versa, however v2.0 cards will not work in v1.0 and v1.0a motherboards"
I have a HD3850 and an intel 915P motherboard, they do not like each other.
Yes i meet all the system requirements, yes PCIe 2.0 is backwards compatable with v1.1/1.0a... but no its not compatable with a 915 chipset.
If you install the card, like me, you will get a UAA HDMI driver conflict. Disabling the onboard sound which also uses this driver won't help either.
Windows now has a thing called ACPI which automatically assigns IRQs to devices on your system. Your old gfx card will be lumped under IRQ 16, this is where the HD3850 will go too. Except ALL HDseries cards have inbuilt HD audio. Making them vga/soundcards. This is a problem for your 915 chipset because it doesn't have the physical resources to assign both the HD3850 and the HDMI audio. Games wont work, you can still surf the net though....