To
Truncate the log file:
Backup
the database (I always prefer to backup first to be on the safer side ;)).
Detach
the database, either by using EM or by executing :
Sp_detachDB
[DBName]
Delete
the transaction log file. (I prefer to rename the file, just in case if
something goes wrong)
Then
attach the database again using:
Sp_AttachDB [DBName]
When
the database is attached, it creates a new transaction log file.
To
shrink the log first backup the log using:
backup
log [DBName] with no_log
Using
Enterprise manager:
Right
click on the database, All tasks, Shrink database, Files, Select log file,
OK.
Using T-SQL:
dbcc
shrinkfile ([log_name])
Here
[log_name] is the logical name of the log file as found from sp_helpdb