Hello everyone!
I just got my Tablo Quad, but totally forgot to purchase a hard drive to allow recording… I have a hard drive at home, but there are some things on it that I want to keep. Can I still temporarily use that hard drive to record shows from the Tablo without formatting it? I had plugged it in when I did the initial setup, but it never asked me to format it…
Thanks for your help! 
the drive needs to be in the format that Tablo needs, so if you want something off of it, take it off before providing to Tablo as Tablo will want to format it.
Part of me thinks you may be in over your head 
As answered, no you can’t. I have recently discovered, despite what’s on the drive or current format (don’t matter) - using the web app (PC browser) or android app, power up the tablo. Access the setting page, the connect and power the drive, within ~30 seconds you ought to get format instructions.
The quick start and instructions tell you to connect everything an turn it on all together. I’ve recently got a second tablo - this didn’t work. Later I changed drives, again, this didn’t work. My experience - tablo first… then drive. Use an app/device capable of initial setup.