"Half-Life - version 1.1.0.8 (it won't update but I also have the latest version running under Steam).
MSVC C++ version 6.0 - no problems here I think
HLSDK latest version"
...I'm afraid HLSDK 2.3 ("latest version") won't work with HL 1.1.0.8. You have to update HL to 1.1.0.9 or downgrade the HLSDK to 2.2
Whistler