Best practice for small Xserve with Macs/Windows?

I confess up front that I am still trying to learn all this, so pardon me for being very new and sounding ignorant. I have installed Leopard Server on an Xserve in Standard Mode and have Macs and Windows machines connecting. So, I have a measure of success. Yet, there are several things just not right and I am wondering if I chose the best way. Would someone mind outlining the way they would have set this up? Here is an overview. I have Xserve Intel/Leopard with 8 Macs (Leopard/Tiger) and 7 Windows XP Pro machines. We have ATT DSL and the modem they provide has a built-in router that we use. We have an Internet domain, but I am not presently interested in it being included in our in-house network (should I be?) Email connects to a POP3 on the domain hosting service we use. These all connect to a 16-port switch. I am basically wanting to do File Sharing for now, then expand to the other things later. I have two 1T drives in the Xserve which are using software raid. When installing Leopard Server I created a domain called "MacServer.bbc" to use internally. I entered the dsl router's ip address in Leopard. Is this the best way to install? There are not that many options in the Standard install (which I am glad for at this point.) Here is what makes me think things are not right: 1) When I try to Connect To Server from 10.5.5 machines, it takes 4-5 minutes to authenticate, though it always does if I wait. From Tiger machines it is near instantaneous. Nor can it resolve the server name on some machines. 2) On Windows machines it has a hard time resolving the name, as well. I have to enter the ip and sometimes that does not work. It seems I should be going through a domain in Windows Networking, but I can only see it through Workgroup. That doesn't seem right for some reason. There are other issues, but I think they will go away if I get this taken care of. I suppose my primary suspicions are in the way I am using the router and the domain. I am reading everything I can on DNS, but most of it seems to deal with Internet, not an internal corporate setup. I would really appreciate any help and feedback in the simplest terms. Also, any books or resources that you would recommend, I would like to know so that I can study them. Thank you, whardy7