Why Windows XP system restore point will be invalid

Q: The operating system installed on my computer is Windwos XP. For security reasons, some system restore points have been established by using the system restore function, but recently I found the restore when using System Restore. The point is invalid, and only some system checkpoints are replaced. These system checkpoints cannot be restored. What is going on here, how can I restore these system restore points?
A: The reason that the system restore point becomes a system checkpoint and cannot be restored is that there is not enough space in the hard disk to serve this function. Generally, when the remaining space in the system installation partition is less than 200MB, the problem you encounter will occur. At this time, as long as some files are deleted and enough hard disk space is left, the system restore will automatically resume the service.