HOW CAN I ENABLE THE SSE ON MY WINDOWS XP?. THE COMPILER IS C++DEV.
HOW CAN I MULTIPLY 3 MATRICES USING SSE2 INSTRUCTIONS?
Recent Microsoft and Intel compilers support the /arch:SSE2 switch. If you're using mingw or some other 32-bit g++, -march=pentium4, and many more recent options, would do it. Choose a method for matrix multiplication, and, if you have questions on it, please be more specific.