I have an acer aspire 5100 laptop that will not boot. Shows boot mgr is missing. The bad thing is it will not recognize the dvdrom or any usb drive. Have a usb cdrom. Bios appears to be corrupted because it did work when vista booted up before, but would not recognize it when selected to boot up in Bios settings. Any ideas on what i can do to get the bios back to factory settings.