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You have to find out what file the error code is referring to It is good that you have the Windows 8.1 installation disk because you need to boot off of it. If your configuration ROM is not setup for that, you need to hit the F2 hotkey several times while you are booting to get into it to change the boot priority to 1. CDROM 2. C: Drive 3. Other. Then use the Escape key to exit, and select Yes when asked if you want to save the changes.
Make sure that the installation CD is in the drive and continue to boot off of it. It will detect the presence of a Windows 8.1 OS, and this should cause it to prompt you to answer whether you want to reinstall or repair the OS. You should choose Repair, if you get that choice. I am not sure of the exact sequence. Just follow the instructions on your monitor.
If it causes the OS to be reinstalled, this can be done without losing any data, unless it forces you to reformat the hard drive. YOU DO NOT WANT TO DO THIS! There are other options, so please stay in communication with me, and I will take care of you.