Remove the hard-drive, hook it up with an external enclosure to another computer and copy out our files. You need to do backups of your files, almost no-one does that properly until it's too late. Now would be a good time to start.
Make sure you are careful and read the prompts as some may tell you the disk will be wiped if you select them. You may want to get someone that knows computers to help you with the repair of the operating system. You may end up needing to do a full clean setup of Windows, or need to get a new hard drive first as some errors are caused by a bad hard drive.