I use Dual Core Processor of 1.6GHz, 512MB RAM, Intel(R) 82945G Express graphics with 256MB. But still, I having low fps like 15 or 16. I already set all the graphic details to low, off and resolution to 640x480, but still I having problems. Whats the main problem here?
If this is still in reference to Counter-Strike Original or any other Half-Life 1 Mod, it is probably to do with the video card as well. Check my suggestions above in regards to switching from OpenGL to Direct3D or vice versa.
The most common issue is because someone's system is setup to one of the above that their system doesn't support. In the past, OpenGL was the best option to solve just about all the graphics issues. With the specs you listed for your system, there shouldn't be any issues besides the video. Either try and update your drivers, switch to one of the options as described above. If none of those work, then the only suggestion I can make is to invest in a better video card, be that PCI, AGP, PCIe (Whatever your system can support)
But for those with older systems that don't have PCIe slots, you best rush out there and dig around looking for anything PCI or AGP, as they have been discontinued by many main companies and even I have found it hard to find just one PCI video card here in the city for my friend. Everything is moving into PCIe.
Also, make sure you have the latest drivers for your video card by checking out the web site of the company that makes your card and see what they have for updates..... this also clears up a lot of big issues.