there are some sempron cpus that don't have the SSE2 instruction set
it was released mid 2004
so pretty much, yeah...your computer is too old to run pro 2.0
you could get
cpu-z to tell you more information about your cpu/memory
if the socket is socket A, you're pretty much out of luck
if it's socket 754, there may be a chance that you could upgrade your cpu to something that has the SSE2 set (semprons should be dirt cheap now)