Basically, any PCIe (PCI Express) card will be fine, though power consumption may be a concern with higher-level graphics cards. The more powerful the card the more power it will draw, and your computer's power supply may not be able to handle it. Unfortunately that detail is not included in the eMachines spec sheet, so I can't give you a specific number. You'll need to peek into the case and look at the label of the PSU (in the top back corner) to find out what its capacity is.
The instructions will walk you through the installation process. It's not quite plug-and-done since you also need to install software/drivers (either from CD or by downloading the latest from the graphics card's manufacturer), but it's not that bad. Just be gentle but firm when inserting the card and let us know if you encounter any problems.
If you report back on your power supply (check for the wattage, like 350W) and your price range and we'll give you some guidance in your selection process.
Let us know.
John
I have an emachins T6212 with an ati200 video card that i want to upgrade as easy as possible. . I know it has an pci express slot, but what card would work and is as easy as just "plug in and done"? I'm not a gamer, I just want to support a better monitor. Recently purchased an HPw2007 because my old monitor quit working.
3200amd athlon 64 , 160 gb hard drive, 512 mb ddr sdram..
Thanks for your help.

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