Question I have a four core AMD X4 840 and windows will only let me select to cores?

We need more information than that. PC brand model or if home built motherboard specs etc. Plus do not use the thread header to ask your question. Type the question where you typed help. Header would be something like "AMD x840 cores problem". So with info right now I would check to see if the CMT is enabled in the BIOS. CMT is the AMD term for hyperthreading.