My partner recently purchased a Nokia Lumia 1020 and gave me his Nokia Lumia 800. I transferred my contacts from my sim card and they all ended up on his phone! I now realise that I have to reset my phone thus deleting his Windows Live account (primary account) and set up my own. He is using the primary account on his 1020. When I reset my 800 will it affect his contacts etc on his 1020? Hope I'm making sense!
Resetting the phone will only remove the relationship between the phone and the previous account. It will also wipe all data on it. The contacts associated with the previous account will not be further updated after the reset.