I was just wondering if this is possible I have a imac 27 inch 2012 running windows 8 could I connect another pc running windows 8 and use both gpus and cpus at the sametime?

Be more specific about what you want to accomplish. You could network two or more computers and share files between them but you can't use both CPUs to speed up running a program by sharing CPU cycles within the program.

Are you running a server farm? Are you running resource intensive programs designed to execute across multiple CPUs? What is it you want to do? If your question is related to running a game faster using two computer's CPUs, the answer is no.

no you can't connect with a computer to another and then get the sum of their hardware in terms of speed

the extreme overhead of the cpu's having to communicate over the network would make it slower then only using 1 of their hardware