If you need/want to keep your database online:

"dump tran <db> with truncate_only" followed by a shrink is very quick too

(do make a full db backup before you start making...

Just make sure you consider memory usage when you move to 1 or fewer instances. Each instance can now use up to 2 (3 if you use the /3GB switch...

Another reason for the transaction log to fill up quickly could be an 'Optimization' maintenance plan ('reorganize data and index pages'). This may cause a transaction log about the size...