You should be good to go with a low-end, low-profile PCI-E 2.0 graphics card. Something like this Jaton Geforce GT620 PCI-E 2.0 graphics card
should work in your system without putting a strain on your 200 watt power supply. Understand, this is by no means a gaming graphics card. This system cannot handle a gaming class graphics card, but any discrete graphics card will work better than just the on-board graphics.
Edit: Also, install the graphics card and then install the drivers for the card.