|In case you don't know, GRUB is a boot loader that is used by many Linux distros. If you're getting a GRUB error, it's possible that someone tried to install a version of Linux & probably botched the installation. If not you, then who?|
Although now that I see the chainloader message, GRUB may have been installed as the boot loader for Windows. Notice what is stated in the following link:
"Proprietary OS's such as Windows 9x/NT/2000/XP, and OS/2 are supported via a chain-loading function"