I Have a dc5800 small form factor, according to this catalog
http://h18000.www1.hp.com/products/quickspecs/12863_ca/12863_ca.pdf
the max power supplied to a PCIe x16 is 25 W, and the aftermarket options for graphic card listed in the same catalog mention ATI HD 4550 256MB, whic consumes around 81 watt at idle levels
What should i do?
Can my PC support any graphic card?
