Thank you all for your efforts. I did try this also, and while the IF condition is important, it is not critical. The bigger trouble is that it does not find the correct sysaltfiles and I get several errors:

Invalid object name 'dbo.sysaltfiles'.

>Hi Boris,
>
>Looks like IF ? in condition is ignored.
>
>I tried
>
>

>declare @Str varchar(800)
>
>set @Str = 'IF ''?'' NOT IN (''master'', ''tempdb'', ''model'', ''msdb'')' + CHAR(13) + 'BEGIN ' + CHAR(13) +
>'ALTER DATABASE ? SET RECOVERY SIMPLE' + CHAR(13) + 'DBCC SHRINKFILE (N''?_log'',0,TRUNCATEONLY)' + char(13) + 'END'
>
>execute sp_msForEachdb @Str

>
>and got
>
>

>Msg 5058, Level 16, State 1, Line 1
>Option 'RECOVERY' cannot be set in database 'tempdb'.
>Msg 8985, Level 16, State 1, Line 1
>Could not locate file 'ReportServer$IOTECHSQL2008_log' for database 'Test' in sys.database_files. The file either does not exist, or was dropped. 
>Msg 8985, Level 16, State 1, Line 1
>Could not locate file 'ReportServer$IOTECHSQL2008TempDB_log' for database 'Test' in sys.database_files. The file either does not exist, or was dropped. 
>DBCC execution completed. If DBCC printed error messages, contact your system administrator.
>

>
>>The same way :-):
>>

>>sp_MSForEachDb 'declare @LogFile nvarchar(2000)
>>                declare @ExeString nvarchar(2000)
>>                IF ''?'' NOT IN (''master'', ''tempdb'', ''model'', ''msdb'')
>>                   BEGIN
>>                      USE [?]
>>                      SELECT @LogFile = dbo.sysaltfiles.name
>>                             FROM master.dbo.sysdatabases
>>                      INNER JOIN dbo.sysaltfiles ON master.dbo.sysdatabases.dbid = dbo.sysaltfiles.dbid
>>                      WHERE (master.dbo.sysaltfiles.fileid = 1) AND (master.dbo.sysdatabases.name = ''?'')
>>                      ALTER DATABASE [?] SET RECOVERY SIMPLE
>>                      SET @ExeString = ''DBCC SHRINKFILE ('' + QUOTENAME(@LogFile) + '', 1)''
>>                      EXEC (@ExeString)
>>                    END'
>>

>>Check for errors, because I wrote this directly here and didn't test it :-)