I've just discovered the smart playlist, which would be a BIG help for parties as I listen to a variety of music, but its not working as I've been building my collection for many many years and the vast majority don't have a completed genre tag.  Its almost impossible for me to complete these manually as I've got over 18000 songs so I was wondering if there is some sort of script I can run which will go through my collection and update my genre tag?

Thanks

If you're using 1.4, all you have to do is go to files, right click on the file holding all the files you want to tag, select Edit Track Information, make the changes you want and then left click on save and close. I find that it takes quite a while if you get over 2-3000 files at once.

Can't tell you anything about 2.x versions.