Why is ms paint not responding?

[tattooedluvintattoosgurl]

When my son opens ms paint, he can work on it for a bit then it freezes and when I try to close the page it says not responding. What is the cause of this? I have vista. So far I have not noticed anything else not working right.
No he is only 6, and doesn't save, he just draws to pass the time away some. It just simply will not work any more.

[TheHumbleOne]

Does your son save the file periodically?
Vista uses a lot of RAM.
Graphics use a lot of RAM.
All the while your son is working in Paint, every move is stored in memory until it is saved to a filename on disk.
After the file is saved, memory is restored.
As your son continues to work, he is again working in memory.

This is why we are advised to save our files at least every ten minutes. You could spend a lot of time on a file only to be unable to save it - I have seen this happen -- or, the program will simply freeze. Most importantly, should the power go out while you are working, anything in memory is lost.