Code:
#include <acknex.h>
#include <windows.h>

typedef int HKEY;
typedef int REGSAM;

long WINAPI RegEnumKeyEx(
	HKEY hKey,
	DWORD dwIndex,
	char *lpName, 
	long *lpcName,
	long *lpReserved, 
	char *lpClass, 
	long *lpcClass, 
	FILETIME *lpftLastWriteTime);
	
long WINAPI RegOpenKeyEx(HKEY hKey, char *lpSubKey, DWORD ulOptions, REGSAM samDesired, HKEY *phkResult);

long WINAPI RegCloseKey(HKEY hKey);

function main()
{
	HKEY hTestKey;
	if(RegOpenKeyEx(HKEY_CURRENT_USER,
		"SOFTWARE\\Unity Technologies",
		0,
		KEY_READ,
		&hTestKey) == ERROR_SUCCESS )
	{
		error("Traitor!");
		RegCloseKey(hTestKey);
	}
	else
	{
		error("All fine!");
	}
   
}



Snippet taken from Prince of Lotteria. grin