when I put my computer( vista home preminum operating system) in sleep mode it shuts down and a few seconds later it re boots spontaneously. Would appreciate help in resolving this problem.
Hi archersown, welcome to NST.
I've never trusted any kind of hibernation since ME, when "hibernate" should more correctly have been named "suspend temporarily then spend 2 days fixing the resulting carnage", so I always set a custom "power saving" environment with aggressively short timeouts on the hardware during use, and power-down completely at the end of the day.
When I first installed Vista in 2007, it did come with "sleep" as a default so I did see the behaviour you mention for a short while till I changed all the power settings.
I believe the most likely explanation will be the way you have your USB power settings