The letter "I" might do what your looking for, for the silent part:
Microsoft(R) Windows (R) 2000 Operating System User Profile Deletion Utility v5.
Copyright (C) Microsoft Corp. 1981-1999
This utility deletes Windows NT and Windows 2000 user profiles.
usage: DELPROF [/Q] [/I] [/P] [/C:\\<computername>] [/D:<days>]
/Q Quiet, no confirmation.
/I Ignore errors and continue deleting.
/P Prompts for confirmation before deleting each profile.
/C Remote computer name.
/D Number of days of inactivity.
But also look at http://www.wisesoft.co.uk/scripts/vbscript_delete_local_profiles.aspx which does the same kind of thing but dosn't use delprof and you can skip certain user profiles.
And if you are using roaming profiles and don't want them kept at all, look into using "Delete Cached copies of roaming profiles" in your GPO's which can be found at:
Computer Config > Admin Template > User Profiles > Delete Cached copies of roaming profiles
although it has been known to fail on wireless networks and such so it might still be good to run either delprof or another script every so often to catch those.