Am new to linux and mythtv but have been doing a lot of reading. Here is my setup and what I would like to do:

Currently have a home network with PC for each child running XP. I would like to rip all their dvds to a hd and allow them to watch it on their PC. I would like to utilize a simple web-type interface for this. Switching their PC's to Linux is not an option. I would also like to do something similar for their music mp3's possibly using Winamp on their pc's.

From what I have been able to pick up in my reading I think this is possible in mythtv. I have toyed with the idea of using DVD shrink and just having them browse to a shared folder with VLC player but would prefer something more user friendly and elegant. Any advice or pointers would be greatly appreciated.

You don't want to use MythTV for this. Just use a samba (windows networking) shared partition. You could make your own webpage for an index if navagating the partition is too difficult. You should play the videos/mp3s over samba not streaming (VLC).

Just so you know, your mythtv box is already running a web server and mysql, so you don't need to set up a new system if you want to create something.

On your local net, you can connect to the web server by something like http://192.168.1.100. At least, many common home routers use the first three and the last one is the first ip address that is assigned.

I haven't figured out a way to just have mythtv be accessible by name yet, especially if the ip addresses are dhcp. I'd rather not add it to the local look up table.

You could always setup a number of "diskless frontends" so that each of the XP machines can be booted off of the network and boot straight into knoppmyth without the need to install anything on them.

You can easily set up multiple diskless frontends. The following should work:

knoppmyth_diskless_frontend.bash hostname1
knoppmyth_diskless_frontend.bash hostname2
knoppmyth_diskless_frontend.bash hostname3

Configure dhcp manually so that you get a fixed IP to mac address mapping for each frontend.

mv /tftpboot/pxelinux.cfg/default /tftpboot/pxelinux.cfg/nnnnnnnn
where nnnnnnnn is the bytewise hexadecimal representation of your ip address. (for example 10.1.1.1 would be 0a010101, or 192.168.1.12 would be c0a8010c).

Copy the nnnnnnnn file for each of the ip addresses and then edit the nnnnnnnn files so that they specify the correct nfsroot location for that host.

have you looked at the mythweb web pages?
You can peruse the list of recordings and download them
from a browser. It was configured and working out of the
box for the last three revisions of knoppmyth.
Just put in your mythtv box's ip into your browser address bar.