Most certainly better than the 6150. The 6150 depends heavily on the motherboard its installed and your performance also heavily depends on the resources of the mother board.
It works with all windows. However you should first check the specs of your present video card to make sure this one is a improvement. If you have a built in video card its already a improvement by freeing up the ram your system shares with the video card.
Correct, Its PCI express for a desktop computer. The video card on a laptop is intergraded into the motherboard and can not be upgraded. They have usb graphic interfaces that allow you to watch TV and stuff like that but nothing that will increase your ability to play games better or run programs that need more power than your video card has now.