There are 6 different groups with this name:

1.) Halloween, an American heavy metal band that formed in 1984. They bill themselves as Detroit's Horror Show. Their carrer spans from 1983 to date.
www.halloweentheband.us

2) Italian heavy metal band (1981-1987).

3.) Halloween, a French symphonic prog band. They existed between 1988-2002 and recorded 5 albums.
http://www.progarchives.com/artist.asp?id=143

4.) Halloween, an obscure 70's Disco-Band. They only recorded one album, "Come See What's It All About".

5.) Hallowe'en, a New Zealand noise pop band.

6.) Halloween, sound effects and music designed for Halloween.

7.) Allen Halloween, a Portuguese Rapper. Read more on Last.fm. User-contributed text is available under the Creative Commons By-SA License; additional terms may apply.