Outta control log file

Customer sez: My log file is 50GB...help!
Kevin3NF: Back it up
Customer: I did, only 46 mb used, still won't shrink
Kevin3NF: Open Query Analyzer, type Checkpoint and hit F5
Customer: ok...now what?
Kevin3NF: Shrink it now
Customer: Hey...cool!
Kevin3NF: That'll be $2.99 please :)

Elapsed time: 4 minutes

We were going to go through the "Dummy table, load it with transactions" bit, but decided to try checkpoint first...