a 64bit version of windows will get u a lot better performance all around and will also allow you to utilize a memory upgrade. Also.. shooters dont rely so much on hard drive speed, but since an HDD is by far the slowest thing in your computer and is a bottleneck for almost all other tasks (especially before anything gets loaded into memory), an SSD will do you wonders. If that is an HDD (u didnt specify) and its only 150gb then that tells me its either a dinosaur or a Velociraptor (no pun intended ), either way it needs to make room for an SSD as ur main drive. Even shitty budget SSDs will blow it out of the water. If u do go that route then u cant lose with an Intel or Samsung SSD for the best balance of reliability, performance and warranty. Other than that, if ur looking for FPS performance then video card is the only thing left.