sorry for my bad english :)
I found embree is very very fast ,but it can not work on WindowsXP,I found a way to run the embree on WinXP ,only modify two source file,hope this can help you
1: condition.cpp,disable the "Condition Variable"(i found the code from the url:http://yats.googlecode.com/svn-history/r74/trunk/src/sys/condition.cpp)
2: sse.h,use "smmintrin_emu.h" instead ""
it works well on my computer