I do have extreme lag too, and its FPS wise. I can dual-client but it lags alot but my CPU has the power to do it, as for the graphics as other's mentioned. I use BitDefender it has a gaming mode to increase CPU Power.
As for others mentioned, Tuneup Utilities and Game Booster are useful, Game Booster is free but you have to register in order to use it. As for Tuneup you have to buy it to use it but it does work.
Their are other free tools that increases performances for a computer, but are usually viruses or rookits so I only trust those who have had programs the longest usually.
As for my CPU, It has 2 CPUs able to handle the capacity of Perfect World, therefore no matter how bad you're graphics is as others mentioned, It depends on how much CPU power Perfect World takes rather then graphic card because I lag desperately in Archosaur but I am still able to navigate my way around there without extreme lag.