i have created a group in activer users and directories and created as user under that group. my os is windows2003 server, i have also created a group policy and i want that policy to be applied to the users belonging to that group only. how can i do that?

Download the GPMC (Group Policy Management Console) from Microsoft and you can have more control over your policy and apply policies not just to OUs to limit the scope to specific groups or even individuals!

www.microsoft.com/downloads/

is there a good tutorial on how im going to implement that?

Get it working? If not, PM me and I'll come back to this. The basic premise is that you have two parts of a GPO, machine and user, and these parts will apply to the corresponding objects in your OU (you can apply GPO/security policy settings to Local, Site, Domain, or OU only but you can use security settings and WMI filters to limit this even further). If you have a "Users" OU that has only user objects in it, then only the user portion of the GPO will be used (such as IE restrictions or folder redirection). If you have a "Computers" OU with only computer objects in it then only the computer portion will be applied (such as assigning software installation or most of the core security settings).