Change Tempdb initial size

I would like to lower the initial size of tempdb.
I have tried running
USE master
GO
ALTER DATABASE tempdb
MODIFY FILE
(NAME = tempdev,
SIZE = 2048MB)
GO

but get error
MODIFY FILE failed. Specified size is less than current size.
thanks

Try this script from books online
--Increase the size of the tempdb device
DISK INIT name = 'tempdb1',physname = 'c:mssqldata empdb1.DAT',vdevno = 100, size = 12800
GO
--Increase the size of tempdb
ALTER DATABASE tempdb ON tempdb1 = 25
Regards,
Sat

For expanding the dafualt logical file tempdev ua can also use the below
use master
ALTER DATABASE tempdb ON tempdev = 25
The above with increase it by 25 MB
Regards
Sat

I guess if the specifies size is less than current size u cannot use this command , as your error ,message states.
I am not sure if restart and rebuild of system database can fix that, I hope gurus have something up there sleeve on this.
Regars
Sat

This worked for me ,
dbcc shrinkfile ('tempdev',6,TRUNCATEONLY)
Traget size in MB = 6
TRUNCATEONLY = gives the reclaimed space to OS.

the tempdb was just created with the wrong size. It was created on our reporting database with the same size as the production DB. The rep DB does not need a tempdb with the same allocated size as production. The reason I need it smaller is that the Initial size is 17gb and is taking up space on disk that is becoming limited.

I am not sure my problem is being understood correctly. I do not have a problem with the tempdb growing too large. It is almost never used. When sql server was installed on this server the settings for the tempdb were copied from our production environment (which does need a large tempdb). Since the tempdb was created at a large size I cannot decrease the size of the database beyond the specified Initial size. The size of the tempdb is 17gb which is unneccesarily large.

Thanks for the replies. I have found a solution to my problem. I started sql server from command line using

sqlservr -c -f
sql server started in minimum configuration mode with a tempdb size of 1MB. I then ran my statement above effectively increasing tempdb size from 1MB to 2048MB (but decreasing from 17GB). after restarting service tempdb size was 2048MB.

This problem is there for not only tempdb but any database, you cannot shrink it beyond the initial size, but I have tried a work around that has worked for me in the past.
Try re-setting the initial size of the data file by increasing it by 5 or 10MB and then try to issue the shrink command, it has worked for me
Satya

I have already found a solution, which I stated in my previous post. It is the same thing and the KB provided. thanks.