Windows 7 has a lot of overhead. One of the more CPU intensive processes that is really not necessary is the RAC task(
https://technet.microsoft.com/en-us/magazine/gg452701.aspx). RAC runs on startup and then every hour and will take a whole core by itself. To disable the RAC task go to task scheduler->Microsoft->windows->RAC and disable the RacTask task. This is one of several things we do to tune our virtual desktop pools so we can run with single cores with out impacting system performance.