Hi there once more!
Well, I solved my problem going through some long steps... Really i thought it was impossible to do it from within MC, and it seems i was right.
First, I have no problems with LAN or media server, I use it since maybe MC18.. at home!
but what happens is that I keep a copy of all my media files on an external HDD to work with my notebook, a portable solution to when i'm out of home (somehow I could never work well with streaming over the net to my library at home. I think it's complicated and slow, and obviously you need net access).
So, I have these 2 libraries, with playlists that mostly coincide but sometimes do not (because i'm always updating them and addin3g new files, etc).
What I did:
1- Export all playlists from PC1 to a folder.
2- Run an external Find & Replace Tool, that can replace strings in a file, and replaced all old file locations with new. Then save the new files.
3- Run an external comparison program (eg. Beyond Compare) and compare the contents of the 2 folders (the old playlists and the new ones).
4- Finding the differences between them, then merging both playlists so that they look exactly the same.
5- In MC, import the new playlist and delete the old, then moving them to the 'playlists' folder, instead of leaving them on 'imported playlists'.
6- et voilá, the playlists now point to the new location and are updated. Now I can create a master library.
this said, it doesn't solve my initial problem: when I want to take my library out with me and all i have is the external hdd, i have to make sure it is an exact copy of the 'home' library...
And also, i had a lot of work to solve something that could be simple if MC had a way to edit the text strings on a playlist...
thanks to all, i hope this helps someone..