Here are your system specs. Although you can use 4 gigs of memory, your XP 32 bit operating system will not use 4 gigs. It may recognize 3.2 to 3.5 gigs at most. If your mobo has 4 slots, you could add a 1gig chip to it and with your current memory, that would give you 3 gigs. As far as a video card upgrade, it appears your machine has a 300 watt power supply and a pci-e slot. The power supply will limit your choices of video cards. If you need a better graphics card, you should upgrade the power supply as well. Look for a power supply that only has one 12 volt rail, like the Corsair line.