Graphics/Video card upgrade for W7 PC

Hi I currently have an old PC which I have done some upgrades to in order to improve performance.

The PC is a Dell Dimension 2400 Series with a processor: Intel P4 CPU 3.06GHz. The motherboard of the machine is Dell Computer Corp. 0G1548 (Microprocessor) and here is a link to its specs: dell 0g1548 mainboard specs.
I have installed Windows 7 Ultimate 32bit and upgraded the RAM to 2GB. The PC runs absolutely fine and smooth on the OS which is a delight but now I would like to upgrade its graphics/video card yet unable to decide which is the right one. I do not want to do any heavy gaming on the machine but use it to watch and stream HD videos from either the HDD or youtube etc.

Judging from the specs of the motherboard could someone tell me what are the requirements I need for my video card eg. slot type, graphic card ram etc. Would something like the following be good enough? : VTX 3D ATI Radeon HD5450 1GB DDR3 VGA, DVI-I, HDMI Low Profile Graphics Card | eBay

thanks.

No that card won't work. It is a PCI-Express (also known as PCI-E) card, and that old motherboard only has PCI slots. You would have to get a PCI card for it to fit the slots. Something like this,

Powercolor Go! Green HD 5450 512MB GDDR2 333MHz x 2.. | Ebuyer.com

is what you should be looking for.

I would suggest this one: Zotac GT610 512MB GDDR3 DVI VGA HDMI PCI Graphics Card | Ebuyer.com

The GT610 is from Nvidia's current lineup and supports DX11 as well.