I've got a quad 550 xeon server running server 2003 and am looking for some optimizations or tips in general. I noticed when doing cpu intensive tasks like decompressing a large rar file my cpu usage only goes up to ~20%.
Most computer activities aren't designed to be run in smp, most are serial operations, like decompressing a file, so no matter what you do it won't use 100 percent of your quad processor system, at most a single task could use 25 percent. The beauty is that a quad can decompress at least 4 files at once, each using 100 percent of a single cpu, and you won't even notice a slowdown.
It really sounds to me like you don't have alot of experience with multi-processor systems. You should hit forums.2cpu.com and read up on them.