10 ControlSet in Registry

Hi there

In my Windows Vista Business registry, there are 10 ControlSets (ControlSt 001, 002 etc) in HKEY_LOCAL_MACHINE\SYSTEM. I just think there are a bit too many (according to some websites a typical Windows installation would have ControlSet 001 and 002 and possibly 003).

Could anyone tell me why there are so many sets there? Also, how can I delete some of them?