I have just reformatted my computer and set everything up again.Just downoaded widows defender and I got a message on my screen telling me to wait until the old version was uninstalled.
Just wondered in spite of a good clean up partioned, formatted, and reloaded windows do some things stay on the drive........just curious .
Thanks in advance

When you reformatted and reinstalled everything, did that include SP2? If so, that included Windows Defender. Then when you went out to get Windows Defender this time, you likely got a newer version than the one bundled with SP2, and the install program detected and removed the old, before installing the new.

If you did a full format (not a quick format) then all the old programs and data would be lost - sort of. Much of the data is still there, but all the spaces that old stuff is stored in is marked as free and available. It would take special forensic software to recover it, and the more you use the system, the harder it will be to recover any of the old. In any case, your current installation would not use any of that old data.

Thanks for your reply.
I did a full format.
Yes! Updates did include SP2.
Ta for the explanation I just couldn't understand what was happening.