i have windows xp sp2 as my os. now if i want to install red hat linux is it necessary to uninstall winxp first ?
what should i do if i want to maintain both winxp n redhat linux as my os ???

Don't know for Red Hat, but for Ubuntu, they install Grub when you install Linux (on another partition, of course), it's a little program that allows you to chose the OS to boot with. I think there is something like this in Red Hat.

If u still wanna use WindowXP for ur work, u needn't uninstall it. U can install both of them on ur pc, install RH on other partition or second hardisk. As moa18e said above, RH will install GRUB on MBR to manage boot menu.

English:

Before you go and install Red Hat linux, defragment your hard drive, so that Windows applications won't get chunks of important data taken out of them. You don't have to delete windows, you can still keep it. Also, if Red Hat doesn't install GRUB then use F12 or whatever key your computer is specified to use to open the boot menu and choose Boot from HDD.

Babelfish French Translation:

Avant que vous alliez installer le linux rouge de chapeau, defragment votre commande dure, de sorte que les applications de Windows n'obtiennent pas des gros morceaux des données importantes prises hors d'elles. Vous ne devez pas supprimer des fenêtres, vous pouvez le garder toujours. En outre, si le chapeau rouge n'installe pas le VER alors emploie F12 ou quelque clef votre ordinateur soit indiqué pour employer pour ouvrir le menu d'initialisation et pour choisir l'Initialisation de HDD.