Update: I adjusted the RAM timings to 4, 4, 4, 12. They were at 5, 5, 5, 12. This has increased the speed to about 5500Kbps. Still way below normal.
I'm running OCZ Dual Channel XTC 2048MB PC5400 DDR2 667MHz Gamer Memory (2 x 1024MB). So it's not bad RAM speed wise.
I find it very odd that 7-ZIP runs so slow especially since it supports multi-threading.