I have an HP desktop and the motherboard got fried during a storm. The system was completely dead. Now, I've replaced the mother board but can't get Windows 7 back. I do not have an installation disk. When the computer tries to load windows, I get a message that Windows is unable to start and that it may be because of a recent hardware change. I've run windows startup repair, but it still won't fix the problem or let me get into Windows. Not sure what to do.