i have register a domain on domain.com and setup my own name servers e.g
ns1.mydomain.com
ns2.mydomain.com

but when i access my page it shows me the following error.....

Great Success !
Apache is working on your cPanel® and WHM™ Server

what should i do next i have never install any cpnale or whm yet....................i also try to putting index.html file in htdocs/ but it not works............

Go to your cpanel click add-on domain and add your domain. You must wait 48 hours before it's start to work.

but i have my own server with xp installed.......and i mentioned that i have no cpanel or any whm installed yet........so what can i do now.......
!!

Add/Replace the files inside your /htdocs/ folder, i think that's the default home directory for Apache