One problem is that the 6670 might be bottlenecked a bit by your processor. The pentium 4 you have is very old, and im assuming is single core. A single core processor isn't very good by todays standards. You would probably be better off building/buying a new computer. The ram you have is not very powerful, DDR2 is not very good for anything today. Most computers run DDR3 memory. Just because you have the correct slot does not mean your computer will work well with that.
TL;DR
Get a new PC. Your components are too outdated for a newer graphics card like that. You will bottleneck your system and won't get the performance you want out of the graphics card. Not to mention the PC you have would be extremely slow for anything but basic windows functions. Sorry, but your computer just ain't ready for a 6670. Get an older model if you don't want to game.