GRUB Error Message #25

I had multi boot on my desktop. Grub brought up a list of distros with boot to Windows Boot Loader with Multi windows distros loaded.
Boot default is Windows XP Pro(family thing with Linux)
Everything was working fine .
One morning Powered up desktop and got Grub error message #25. All I could find out was go to linux rescue disk and reinstall GRUB.

That sounded like a WINDOWS fix!

What's a #25 & how to fix???

JT