I have a pretty old (2001) semi-custom built computer running win xp for a while. One day it just stopped working. The hard drive was stopping and starting, so I thought that it was just dying. I put in a spare drive and loaded win xp and then got the dreaded "error loading operating system" message when it rebooted. I tried this again and also with two more drives, all with the same result. These were all small drives (40GB or less), so drive size is not an issue. Out of desperation, I re-installed the "broken" drive and it is working fine for the moment. I have re-installed xp on this computer many times in the past and never had this problem until now. Any suggestions on what is wrong? I'm afraid it might stop working again without warning.