I have a HP Pavilion a1120n Desktop PC. I was planning on giving it a motherboard with pci-express like the ASUS A8N-SLI ATX($135), because right now it only has pci and no agp. Currently using FX5500 OC 256 pci card. First, can it fit within my comp? Second, am I able to keep what I have on my harddrive with windows? Or do I need to buy windows to and have to start from scratch again. Here are pictures of my case. Also can give me ideas on what I can do to modify this case.