HKEY_CURRENT_USER\\Software\\Valve\\Counter-Strike\\InstallPath
HKEY_CURRENT_USER\\Software\\Valve\\DOD\\InstallPa th
HKEY_CURRENT_USER\\Software\\Valve\\Half-Life\\InstallPath
HKEY_CURRENT_USER\\Software\\Valve\\Steam\\ModInst allPath
That's all the reg keys i know of for HL