sql server xp_delete_file deletion files

i'm perplexing sql mislay files form '.7z' comparison 7 days.

here's i've got that's working:

declare @datestring char(8)
set @datestring = convert(char(8), dateadd(d, -7, getdate()), 1)
execute master.dbo.xp_delete_file 0, 
                  n'e:\database backups',n'7z', @datestring, 1

i've also attempted changing '1' a finish '0'.

this advantage 'success', nonetheless files aren't removing deleted.

i'm controlling sql server 2005, standard, w/sp2