yes... you CAN upgrade the processor, bought an intel dual core 2.0ghz , swapped my single core 2.16ghz and made a remarkable difference... i found the processor for less than $10 on ebay. (used) , and took to my handy work of disassembling. it took me roughly 1 hour, with a little experience in pc background. for a newbie. to carefully do this - 2.5 hours. and well worth the time invested to update a computer for a little more power.
You definitely can upgrade the Processor. you can download the maintenance guide here:
I found a AMD PhenomII N930 Quad core for $75, upgraded the ram to 8 gb and i am easily running windows 8 pro 64 bit with out any issues what so ever.