This is what I've used for a long time:

DECLARE INTEGER GetSystemDirectory IN Win32API AS GetSysDir ;
	String @cBuffer, Integer nBufferSize

pcBuffer = SPACE(199)
=GetSysDir(@pcBuffer, 200)
pcBuffer = ALLT(STRTRAN(pcBuffer, CHR(0), ""))
IF .NOT.EMPT(pcBuffer)
	lcWinSysDir = pcBuffer
ENDIF

>I am trying to develop an application that will self-distribute itself and install the OCX and DLL files it needs but I don't know what syntax is or function to call to locate the System directory of the OS to copy these files to. I cannot use the Setup Wizard to generate the setup files or to install the OCX and DLL files. I need my application to do it. Can someone help me on this one?