That motherboard has one PCI-E x16 slot. So yet it will work.
HOWEVER - You need to make sure your Power Supply is up to snuff. The GTX 260 requires TWO 6-pin power connectors, and can draw a decent wattage (182W TDP). Can you give us the model number on your power supply?
MCP61PM-HM Motherboard @ HPhttp://h10025.www1.hp.com/ewfrf/wc/document?lc=en&dlc=en&cc=us&docname=c00906137#N1253