Dedicate A CPU Core To A Single Process

I have a 2006 single-threaded game that sometimes uses 100% of one core. I have a 3 core AMD CPU.

Will dedicating a core to the game boost the performance a little bit? Or is Windows 7 is already automatically moving processes to another core when one core tends to be saturated?

How can I dedicate one core to the game without having to manually set all the other processes to use only the two other cores? Is there a way to pre-set the core affinity before a process is run? (Windows System Resource Manager seems to be able to do this, but there doesn't seem to be a version of it for Windows 7) Maybe defining the game priority as Real Time would achieve the same effect? Or is there a risk that this would hang Windows and other processes?