Why is there so much lagging going on in the Game???

Hello friend. it depends on the game. Keep in mind that it might be just one of the components or all of them. For instance, loading the game depends on the processor and ram. Lagging during the game, after loading screen, considering you have 2 giga of ram, is basically because of the vide card, a 7800 GS (you haven't mentioned what type it is) is kind of outdated in our days, and by this i mean the newer games. However, it might be all of the components, like in Gothic 3's case, where you need a very good computer, and to get all the updates. Try allocating more virtual memory (you should have at least 4 Giga of HDD memory, with the chance of it increasing to 6 or 8, just to be sure.).

It is based on what game you are playing. If you are playing games like Crysis, it surely won't be enough. The otherwise goes for smaller games like flash games. But, I think if you played games like World of Warcraft or Call of Duty, it surely be enough. If it is the case, it maybe caused by background activities in your computer. Try stopping any background activities using your task manager. I think it will help.