In a Windows environment that has a high number/size of files/dirs being deleted, a 10% build time improvement has been seen after the Recycle Bin properties were modified on both the Electric Make and Agent machines.
To configure this option, highlight the Recycle Bin icon and right click the mouse. Select properties from the menu. On the Global tab, check the box that says "Do not move files to the Recycle Bin. Remove files immediately when deleted."
Please note that the overall performance improvement depends on the number/size of files/dirs being deleted, the size of Recycle Bin and how full the Recycle Bin already is. Inthe environments that saw the greatest improvement, the sizes being deleted are in the range of gigabytes.