Reusing an old HP Compaq dc5700

Hi,

Not sure if this is the right forum, but here goes. Recently I've inherited a dc5700 Microtower http://h10010.www1.hp.com/wwpc/ca/en/sm/WF06b/12132708-.... I had the intention of building a mid-range gaming desktop from scratch but was able to get this for free. I'm very new to home building, but I'm up for cannibalising to whatever extent. Is it even worth using this computer for the case, replacing most other parts including power supply and motherboard, if I want to install a GTX 670 and an i5-2700k? Or would I be better off going from scratch?

Thanks