SA,

You cannot delete the primary log file, which is probably what you have.
You can shrink it by using:

DBCC SHRINKFILE (Database_Log, <size in megabytes>)

For guidance, see: http://www.karaszi.com/SQLServer/info_dont_shrink.asp

RLF

DROP DATABASE. Yes, that will get rid of the entire database, but
that is exactly what you are asking for. Never delete a log file, unless
you want to lose your database.

First decide what kind of recovery you need in case of a disaster. Are
you content with restoring from the last good backup? Or do you need
up-to-the-point recovery. In the first case you can set recovery to simple
and then use DBCC SHRINKFILE to shrink the log to a reasonable size, for
instance 1 GB. (But what is a reasonable size depends very much on how the
database is used.)

If you need up-to-the-point recovery, you better study closely how
BACKUP and RESTORE works, because right now you are heading for a disaster.

smca

Well, Rassel and Erland have alredy answered you.  I would like to add

Erland is correct, you need to drop the database , as  you said 'an old' log
files means that db is not in used anymore, right?

However , if  the db is still in use you need
1) BACKUP LOG file
2) DBCC SHRINKFILE