Since the drive is accessible with the enclosure, it may be okay. Having Windows installations become completely garbled is nothing exceptional. Since you now have the enclosure, you can format the drive when you have copied everything valuable and keep it as an extra data drive. If it has any bad sectors, those will be marked during formatting. As it is an old drive, don't rely on it to store anything important, but you can use it for temporary or back-up storage. Be absolutely certain that you do not accidentally format the wrong drive!