i have a diamond hd 3450 video card and went to put into a hp with a msi motherboard and when i took out the nivada video card the asus would not fit into the slot??????
If this is your board then you are correct. You have a PCI-Ex16 graphics card slot which is not compatible with any AGP card. Return the HD3450 (if you can) and get a PCI-Ex16 version.