Start by buying a second NIC card (please search the forums and wiki for "2 NICs" or similar, you will see this has been discussed to death, and all the reason why you need 2 NICs, in particular the FAQ on the wiki)
Plug the "external" or NIC 1 into your existing network and allow it to get an IP address from your DHCP server.
Relocate your Vista machine to the "internal" or LMCE network - either by plugging it into another switch/hub and also plugging the "internal" or NIC 2 on your LMCE box into the same hub/switch; or by plugging your Vista box directly into the second NIC of your LMCE machine (most NICs these days do auto crossover so this is fine)
Before you do the relocation, make sure that your Vista box is set to get a dynamic IP address from a DHCP server, not statically set. LMCE will fullfil this request for your Vista box, and at the same time, discover it, its shares, etc and add them to your media database.
Before you do that (probably best to read this email backwards!) you should have a share setup on your Vista box to host all your media. When LMCE discovers this share, it will ask you if you want to use LMCE's folder structure. Say yes to this - it will then create the folder structure on your Vista share. Once it has done this, you should relocate your media into the appropriate folders it has created for you. LMCE will then discover your media (takes a little time) and add it to your media database.
There are other ways to do this, but relocating your media into the standard folder structure is by FAR the best way, and will prevent you having to come back and ask how you access your media because you can't see it within LMCE (believe me)
