On start-up Windows gets as far as "Loading personal settings" then the screen goes blank and locks up. It then requires a power down and cold start to load properly. The system will then work properly for a short time before the mouse starts behaving strangely and everything becomes very sluggish. Apart from a possible virus can anyone please come up with any other suggestions. This is not my own machine and I am very hesitant in reinstalling a new version of Windows unless it is absolutely neccessary.