uninstalling RH9 will delete the GRUB, a major prb when you have dual OS.
 

I have installed RH9 yesterday without knowing that it is no longer supported.

can I update to any other version of RH or any version of fedora.

if not and I have to reinstall a different distro.

how do I uninstall RH9 and install a new distro without having the common problem with the GRUB. (when you uninstall linux The GRUB is deleted and you cant access your other OS. widows XP for example).

You don't need to "uninstall" RH9 - the installer for the newer distro will do that for you. The installer will also install a new GRUB to the MBR. Most modern distros will automatically recognise the windows partition and configure GRUB accordingly.

Note: you will not be able to "upgrade" from RH9 to any fedora. There are too many differences.