Not necessarily, a number of C2D/C2Qs and most Xeons (based on the C2D/C2Q cores) have that required functionality... (VT-x being the main one for HyperV in 2012).
If your C2D/C2Q has VT-x, I would surprised if Win8.1 doesn't work on it. (As VT-x includes PREFETCHx, LAHF/SAHF, NX, Intel64 and...