Secure delete problem with NAS device

When I delete files from my NAS device or USB pen drive, opus always uses secure delete no matter what delete option I try. Is there any way to stop this or force Opus to use normal delete like windows explorer?

Is Preferences / File Operations / Deleting Files / Use Secure Wipe turned on?

(If it's on, turn it off, of course.)

If not, which delete button/menu/command are you using? Has the command been modified, and/or are you holding down Shift when you use it?

Many thanks Leo, I had the secure delete checked in prefs. I thought turning this off would prevent secure delete on other operations, but is still works with this option off. All sorted thanks a bunch.