I thought I remembered a flag, but if you use intrinsics (_mm_div_ss and __m128 etc), then just #include "xmmintrin.h" (use chevrons) for SSE2 support.
If I can find an old project, I will check but if you prefer vs6 (as I do), you can use the Intel compiler.
Although I use 2005, 2008 and 2010 at work on a daily basis, vs6 is my preferred option for working on a netbook on the go.
I also recommend Perforce free 2 user version for local backups with vs6 integration.
By the way, only install sp5 with pp5, sp6 has no processor pack.