You can use the Beatport Downloader application to give you some control over how the files are named, including removing the catalogue number. It still doesn't give quite as much control as I'd like (for example, if you want to have artist, track, mix and label in the filename, you have to put the label after the artist), but it's definitely an improvement over downloading through your browser.
The number in the file name makes no difference to me. I use the Beatport Downloader to download all of my newly bought tracks at once. Then U use mp3tag to get the metadata how I want it and automatically rename my mp3 files.
Aug-07-2010 15:15
trancypantzzz
Supreme tranceaddict
Registered: Oct 2009
Location: New Jersey, USA
it's the track's id number in the beatport database.
Aug-07-2010 15:55
Teezdalien
Supreme tranceaddict
Registered: Jul 2007
Location: Melbourne, Australia
Can't you just remove it in the files properties? Is it really that difficult?