System Recovery for Optiplex 380

I seem to have hit several brick walls.  Perhaps someone can point me to a procedure to get me through, or enter the steps I need to do that.

I have W10 installed on the computer but would like to restore it to the factory W7 OS.  (Is W10 causing part of the problem?  Doesn't seem likely since at boot time I am loading the Repair Disk OS.  But/and the factory recovery partition is no longer present!)

I had created the recommended bootable "Repair Disk" (CD) and the "Recovery Partition" (DVD-RW).  (I have found one comment that a DVD-RW will not work for this.  Can that be?  It burned with no problem.)  From what I understood when I created them that with that pair of disks I could restore the computer to as delivered state.

I have tried the F8 entry to system maintenance, with varying timing, many times.  It is always ignored and I always wind up in W10.  It seems to have been disabled in the BIOS.

I can boot to the Repair Disk but wind up in several rabbit holes as it tries to find things on it's own.  If I persist, I can get to the "System Recovery Options" window.  At this point, the rabbit holes seem to all dead end.  If I select the option "Dell Factory Image Restore" the system cannot find a recovery image.  I can't force it to select the image either from the DVD or from C: where I have copied it.  Even through the advanced options, since the system refuses to find the DVD, C:, or any of my network devices.  It goes so far as to prompt me for the password, but never finds the device after that.

I have searched many posts for the exact operating procedure to follow for recovery from this pair of disks.   But all that I can find, even on the Dell website, either assume the F8 entry will work or that I have a Dell "Reinstallation DVD" (which did not come with the computer) , not the CD/DVD combo I produced when I bought the computer.  (Those, by the way, look fine if examined by Windows Explorer, and as I said, the system does boot to the CD.)

I sure would like an idiot-proof step-by-step to revert to factory settings using the CD/DVD pair that I have produced.  Can you help me?

Thanks