MSDE backup file is appending

Question

I have an MSDE 2000 database backup file which is appending rather than deleting or renaming. I am using this command: BACKUP DATABASE [SPSDB] TO DISK = 'E:\Program Files\Microsoft SQL Server\MSSQL\BACKUP\SPSbackup\spsdb.bak' with retaindays = 1

I am using a maintenance plan on my full SQL version databases, and they create a new file everyday with the date in the file name.

The backup file size creeps up on me if I don't monitor it. Is there a way to have MSDE make a uniue file with the daily backup job I created?

Thanks, Chad