i have redhat linux 9.0 installed on my system. i want to install windows xp as a dual operating system. i know that it is possible to install linux after windows xp is installed. but i need to install windows xp now. how to install windows now.

Do you have any free space on the hard drive you're installing Windows on? If not, you'll need to resize your Linux partition. There are utilities that can do this, such as QtParted and GParted. Once that is done, just proceed as normal with your Windows installation. Be aware though, that Windows will overwrite the MBR with its own bootloader. So, in order to boot Linux, you'll need a boot floppy (or if there's a way to reinstall the bootloader from the CDs). After that, just edit grub.conf/lilo.conf as appropriate and add your Windows partition to it.

Edit: damn it, I took all the time writing a reply .

Don't forget to backup your installation just in case something goes wrong with the resizing.