I Need Your Help. What’s The Best Way To Sync Folders Between PCs?

I have a problem that I’m hoping a reader might be able to help me with. I now have a dedicated Home Theatre PC which is connected up to my plasma TV and home cinema system. I also have my main PC which holds all my music, DVDs, photos and videos.

Because I use the HTPC mainly to listen to music and to watch TV, I’ve decided to keep a complete copy of my music collection on the HTPC, so that if that I only have to switch the main PC on when I want to watch a DVD.

The problem I have is that I use my main PC to manage my music collection, so I need a fast way to sync any changes between the folders that contain my music on the two PCs e.g if I add a new album to the main PC or fix some tags or create a new playlist, I can somehow automatically sync that new album/update to the music folder on the HTPC.

I haven’t been able to find a good sync program – can anyone recommend one that works well? Or, maybe a way to sync folders using Vista?