Sharing Between Vista and Leopard

My head literally hurts from all the reading I have done on this forum. I am
usually pretty tech savvy, but this has me completely stumped.

I have a Macbook running 10.5.2 and a PC running Vista home pro. I recently
purchased a new computer to replace my old one and that is when the trouble
began. With XP, I was able to share files back and forth between my Macbook
and my PC. The PC is wired into the router while the Macbook connects
wirelessly.

After buying the Vista-based PC, my Macbook no longer shows the PC in the
network. The Macbook settings, largely unchanged, are sharing files,
printers and bluetooth. I have two users on the Macbook, one of which is
identical to the only user I have on the PC. I have verified that the files
and printers are listed under the shared files on the PC. I have also
changed the lsacompatibilitylevel from 3 to 1 as instructed in other posts.
I have Norton installed and have run through the network settings time and
time again. Finally, I set them to the least secure as possible just to make
sure Norton wasn't the issue. The only thing that has changed is XP to
Vista. I am not a hater of Vista like some, but this is an important feature
that worked effortlessly and flawlessly in XP. Why did MS have to mess with
this?

I really appreciate any help I can find. I am not looking forward to trying
to replace Vista with XP.