Yes, it is very possible. That drive is pretty outdated, and if its getting full, of course that makes a huge difference too. A nearly full, fragmented drive can literally crawl with slowness. I am not sure about the NFS2, but you do know that not all games can make use of multiple cores, so unless the game is written to use 4 cores, unlocking the last core probably is not much help at all for most games. In your specs you also list a green drive, and while the power saving features are nice, they are not really great for performance or gaming.
Well half empty or full it performs the same. I feel like its going to die any moment. Windows 7 rates it at 5.7 and all my other components are above 7. CPU: 7.5, RAM: 7.9, GPU 7.8 and the hard drive is 5.7 xD