acSendKeys("@") --Sends a single keypress (Down and Up) of the Windows key
acSendKeys("{VKEY 91}") --Also sends a single keypress (Down and Up) of the Windows key, using the VKey
acSendKeyDown(91) --Sends only the down command (press) for the Windows key
acSendKeyUp(91) --Sends only the up command (release) for the Windows key
The StrokesPlus Help page explains all of the above:
http://www.strokesplus.com/help/#acSendKeysUsage