I've never built a computer before, i want to. I want to be able to play good computer games, Doom3, Half-Life2, etc. But my computer won't. Store Bought Intel Celeron 2.8ghz, 512mb DDR Ram, Ultra Speed CD Re-Writer, DVD 16X viewer, 120gb Ultra DMA Hard Drive, but i have no AGP slots, nor PCI Express, just old PCI slots. Can i keep my hard drive, cd writer, and dvd viewer, but replace my processor and motherboard?