Is it possible to upgrade a graphics card in a small computer case?

It is possible you have to install a "low profile" video card, and one that does not need a lot of power, since upgrading the power supply is probably not an option. In effect, you have a severely crippled system, not suitable for upgrades. Low profile cards: http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007709+600038363&QksAutoSuggestion=&ShowDeactivatedMark=False&Configurator=&IsNodeId=1&Subcategory=48&description=&hisInDesc=&Ntk=&CFG=&SpeTabStoreType=&AdvancedSearch=1&srchInDesc=

you need to look for low profile graphics cards

I really do not think a GTX 560 or Radeon HD 6850 would fit inside that case. You also need a power supply that has enough wattage and connectors for a large video card like that. Even if you did get one of those cards, your weak processor would bottleneck your performance unfortunately. If anything, I would recommend a GeForce GT 520 low profile card. It is not intended for gaming, but would do significantly better than a GeForce 7100. Either get a nice low profile card or save up for a new computer. :) EDIT: Sadly, a 8800 GT is even bigger and consumes more power on the older tech. :( But that low profile GT 430 looks very very nice. Now you would have to find out if you have a power supply that can handle it. According to this calculator, it would require one that is at least 261 W http://c1.neweggimages.com/BizIntell/tool/psucalc/index.html?cm_sp=Subcat58_PowerSupply_left-_-PowerSupplyFinder022610-_-http%3a%2f%2fpromotions.newegg.com%2fproductfinders%2fpowersupply.jpg Open up your computer and look at your power supply. With any luck, it might be 300 W or 350 W. It should say right on the label.