By default there are 6 files. You won't be able to delete the active log and to be honest you shouldn't be messing directly with files that SQL works with.
Why do you want to delete them? To cover up something that is logged in the error log that you don't want others to see? Or is the current log just too large and you want to create a new empty log?
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability