I don't know of any programs for Windows, with one alpha-version exception, that does the same thing as Paint (after all, why bother?). I do know how you might be able to fix it.
Open up a Command Prompt (it should be in Accessories), and enter this command:
This will check for corrupted system files (Paint is considered a system file) and will try to replace them. It may need to copy the files from your Vista DVD, so be sure to have it handy.