There are lots of software programs that would do the trick for you.
Cakewalk, N-tracks, Samplitude, Acid. The list is big.
I use Acid Pro 4.0, and load my tracks with the WAV convertor from Roland. It works great, and is very easy. You wouldn't need a Mackie for mixing with any of these programs.
If you are recording real drums and are using several mics, then a mixer would be needed because of the BR8's lack of multiple inputs. Thats not a problem for me as I use a drum machine.
You have to realize a couple things when doing this. First, the tracks you load via the convertor won't transfer effects from the BR8. This is not a problem as any decent software program has all the effects you need. Make sure you get a program that supports DX plugins. Then you can use plugin FX from any company in the one program. Also, you can load your 8 tracks, mix 'em, and transfer them back to a stereo WAV file that can by converted with the Roland WAV convertor back to a BR8 file (2 tracks/L & R) Then load them back into the BR8 and you have 6 empty tracks to work with again. This can be done indefinately so the Zip drive space is not an issue anymore.
You can try N-track for free at
www.fasoft.com. Its a good program and I think it's only like $35.00 for the full boat. Its a nice start.
Good luck
Joel