Hello steve, i have had sooo many questions like this and they are very simple to solve. Firstly see if you can get another windows installer disc, i lost myne once and i calld someone out and they gave me another one, if its not that it needs re-instaling your motherbord could be on its way out, you can buy motherbords but they are tricky to replace for beginers, hope that helps mate
sam the pc man, May 2009