Is there a way to reset Windows file cache?

Legendary programmer Mark Russinovich has created a large number of tools that must be in every Windows administrator's and developer's tool kit. One of those tools is RAMMap. On Vista and later (and 2008R2 is later), RAMMap will allow you to free selected memory pools.

The option you want is Empty -> Empty Standby List -- cached pages that are clean and thus eligible to be freed will be in the Standby List. Note that you won't see anything happen in the RAMMap display because it doesn't auto-refresh. You can hit F5 to refresh the display or watch in Task Manager or another tool.