Gingernut, If your system is an XP variant, get hold of a system disc, licence details are not needed for this procedure. Insert CD, and allow machine to boot. When disc gives a couple of options, (install or repair I think) setlect R for repair, and when the comand line appears, enter fixboot, followed by fixmbr. Answer yes if asked. this should repair the boot sector and boot information. Exit , and allow to restart. Hopefully this may fix things.