My computer was on but did not respond out of sleep mode when I tried to access it. I had to shut it down manually and when I turned it on it told me a file was missing. I put my Windows XP home edition upgrade CD into the D: drive and it uploaded some files. I then got it to run the check disk utility like it was starting up normally but after that it told me there was an error and now it tells me there is no operating system. I'm not sure what happened but I really hope there is some way for me to use my computer again. I am not really worried about my files because I have a backup of the important ones. I just want to know if there is a way I can reinstall or start the computer using my Windows XP upgrade cd. Any help would be appreciated.