A computer can have two processors if they are in the same physical unit.
Computers with two separate CPUs are uncommon because it slows down how often information is shared by both CPUs. The more often that information is shared, the faster programs run and the better they handle multitasking. Studies show that this type of single-CPU configuration can slow down performance to half speed for some programs, while computers with one processor might only see a 10% slowdown in performance.