This is probably old hat to many of you, but I have just started upgrading some of my older kit.
I bought an ASRock MoBo and an AMD Phenom II x2 560BE processor.
Build went OK and I went into the BIOS and changed a few things.........next time I look I have a Phenom II x4 B60????????????
Looking around a bit it appears that a 4 core Phenom probably has 6 and that a Sempron certainly has 2 rather than the 1 that it is sold as. This one I bought as a 2 but actually has 4 according to CPU-Z and speedfan.
Apparently not all the cores may be capable of being enabled, and your chances are better with boxed and black (unlocked) editions?
It actually makes Vista perform well