2 things I'd try as long as all previous partitions on HDD/SSD were deleted before reloading OS as redxps mentioned: How to Perform a BIOS or CMOS Reset and Clear the NVRAM on Dell Computers  How to use the jumper to reset the BIOS password on your Dell desktop computer  Even if I'm not 100% on target with the 2nd option, I'd still try if the first option doesn't work. Something is obviously maintaining AT&T's memory, so hopefully the first option works.  With PC unplugged and battery removed, be sure to push power button to make sure all power is drained. Before doing any BIOS resets, you may want to note current settings, like SATA Operation, so that you're not having boot problems afterwards.  Just an example of the SATA Operation screen below: [IMAGE] Normally, it should be set to AHCI.  However, you want the same settings your boot drive was loaded in.
I bought this 5070 on Ebay with the proviso that I would have to find a a workaround to get past an ATT services login screen. (see below). I figured it would be easy to re-partition and re-format the drive, then reload the os using the windows 10 media creation tool..but NOPE. To my ever loving surprise the login screen came right back. I've used diskpart and clean all to try to get rid of it, but it keeps coming back Does anyone know a workaround? It seems to be embedded in the hardware somehow.. [IMAGE]
Can't get rid of ATT services login window.