Lets clarify... you only want to remove the boot option for windows, right (not the entire windows thingie)? If so, go edit your /boot/grub/grub.conf and comment out any lines regarding windows.
You'll probably find something like this:
Code:
title Windows something
rootnoverify (hd0,0)
chainloader +1
Right, so just add a # at the beginning of each of these lines or delete'em (I'd just comment in case needed in the future
)
Note: This works only if you use Grub as your bootmanager. Dunno what distro are you using, could be different.