Hi Andrew
Okay - I am using version 6.07 and this is how I would probably do it.
In the Delete File Task, under the File Filter Tab, there is another (sub) row of tabs. One of them is 'Date'. If you select this you have the option to select 'Created date' or 'Modified date' being either older than or newer than a particular date. You can use the system date variable {DATENOWADD(Days|-7|dd/MM/yyyy)} and although it is called DATENOWADD, the value -7 removes 7 days from todays date.
Hope that was what you were asking?
Cheers
Andy