Virtual-Hideout posted a review on the Patriot PC2-6400LLK 4GB Memory Kit

One thing that can always make a computer operate like a new machine is memory. If you've ever used your system with the bare minimum amounts of memory or just enough to get the job done, then you've held your system back and probably noticed lots of lag. Plenty of system memory means your machine will perform much smoother with little or no lag. This is especially true with today's Windows XP Pro or Vista running these huge new games like Crysis and Call of Duty 4. The larger the data amount, the quicker the access and read times seem due to the extra memory.

Patriot PC2-6400LLK 4GB Memory Kit Review