The immediate symptom is that a file needed to start Windows has been corrupted. It is entirely possible that a repair of the Windows operating system will correct the problem; HOWEVER, the hard drive itself may be the cause of the problem in the first place. The hard drive may be wearing out. This does not mean that the files on that hard drive are not accessible.
There is a very simple (to computer guys/gals) old trick to get to these files. You remove your hard drive from your computer and add it as a second drive in another computer. Given that all computers involved are running Windows XP, there should be virtually no problem in your drive becoming readable. It will be there in "My Computer" as a second hard drive.
At this point, your personal files should be accessible.
One may ask, "If her hard drive is so bad that it can't run Windows, why would it magically work okay in another computer?" Valid question. Here is the answer: The hard drive in this case has only become partially defective. The defect is in reading the most used area of the hard drive: the Windows operating system. The personal files are not being continously accessed as Windows is and that physical part of the hard drive is likely still okay.
Once this is all straightened out, perhaps your brother would be kind enough to partition your new hard drive into two virtual hard drives: one for the Windows operating system and the other for your personal files. In that way, should Windows ever go bad again, you are able to reinstall the operating system all over again without endangering your personal files. That's how I have my system set up and even though I have had computer and virus and other problems, I have never lost a bit of my personal data.