As topic say, I'm having problems with steam games I didn't know where to post this well I guess some nerdy can help me here (: First I would start off telling my specs (Bad) :
System Manufacturer: Hewlett-Packard
 System Model: HP Compaq dc7600 Ultra-slim Desktop
 BIOS: Default System BIOS
 PROCESSOR: Intel(R) Pentium(R) 4 CPU 3.00GHz (2 CPUs), ~3.0GHz
Memory: 4096MB RAM
Available OS Memory: 3320MB RAM
DIRECTX Version: DirectX 11

Soo Why can't I play steam games, I only got 9 Gb FREE space Total 37Gb On hardware Dunno how to get more make it bigger or usb maybe ? PLZ answer fast (: Ask anything feel free.  You've enough space to play steam games. I strongly suspect that the problem is with your Video graphics driver and updating it might address your issue. Do visit the manufacturer website and try updating it to the latest.

Also, check for any available updates for running OS version and install it ASAP.

Share your progress!I try to ACCESS at steam games. It works in my computer. I'm using HP computer too. The only difference is our model and spec.
I would suggest that you upgrade your video card memory to 2gb to play in steam games. Since the plug-in is updating often.What happens when you try and launch a game?

Your machine is very old so I imagine it's simply too old to run modern games, what sort of video card are you using with it?You haven't listed you GPU in your specs, the component that is the most decisive when asking about being able to play games. Juding by the cpu it's paired with i'd say its too weak to handle any. But yes most problems like these originate from outdated draphic drivers.