assuming you mean the playlists shown in the playlists branch of the tree in MC, rather than actual .m3u files you created, you would be looking for the playlistx.jmd file from the old MC library folder. It contains all your playlists, smartlists and groups.
The media files would need to have the same file addresses now as they did before. Go to your \Documents and Settings\user\application data\J River\Media Center 12\Library\ folder to find the old file and copy it into the same location on your current drive, making sure you have a current library backup in case of unexpected results, and also that MC is closed at the time. When you start MC, the playlists node of your tree should be back to its former state.
Of course,
if your media files are all in the same location as they were before the crash, there's nothing to stop you restoring from a library backup. Unsurprisingly, you can find these in the \Documents and Settings\user\application data\J River\Media Center 12\Library Backups\ folder. MC creates these automatically for you and places the date in the backup filename.
Choose the file you want, then open MC and click on the
File item in the top toolbar, then Library, then restore library. The dialogue opens at the default save location. Use the "Look In..." field at the top to browse to your chosen backup file and select it. This will restore everything, not just the playlists section of the tree and if you have the option,
this should be your preferred choice 
If your files are not in the same location, it could still be possible to restore from a library backup, but more work would be needed afterwards. How much depends entirely upon what the file paths used to be and what they are now.
Good luck.
-marko.
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Topic: Playlist files/location (Read 8556 times)