Can you say what you mean by 'enabled dual booting'?
If a system is able to co-exist with another it will normally pick up the details of the other's boot files and create a boot menu automatically. I have no experience of server 2003 (on a laptop!) but can only suggest downloading BCD or Vista boot pro which should allow you to reconfigure the booting arrangement to dual boot.
Basically what is needed is for both sets of boot file to be on the same partition normally in the first primary partition, which clearly didn't happen with your installation.