usb problem, pc turn off!!

Hi all,

There has been a problem in my pc, whenever i enter a usb and there is activity on the usb for ex. a wireless adapter and im downloading from the internet, or a flash drive, and im copying something on it, my pc turns off as if there is an electricity failure, interestingly, i have turned off the usb 2.0 support from the BIOS and this problem has stopped occuring, but of course the usb is much slower now,

any ideas would be really helpful,

Could be a power issue. USB2 allows USE deviceses to draw more power than USB1.

Other than that, check your PC maker (or MOBO maker) for chipset updates.