^ see title^
Tag and Rename, great piece of kit, you can probably find it on Download.com or tucows.com IT can check all existing tags, and even guess names from your MP3 file names.
I think the demo is free and full functional for 30 days or something. Although, judging by the website, it's just free!
Edit: Damn your nimble fingers Big Bear Ah well, at least I know I'm using the right toys!