back to NT 4 domain

HI,
I want to upgrade my NT 4 domain to 2k server .First I will promote one of my BDC to PDC and then I will upgrade it .I will put one of BDC`s offline during upgrade .The question is : If I did some thing wrong and I want to get back to NT domainenvironment ,is it possible to shut the 2k and put the offlined BDC online and then promote it to PDC ?
Thanks.