OK, I've done my Backup and restoration using BESRO 8.5 to a different server, Serve B is now running using new hardware and now I'd like to reformat Server A this time without BE tools at all because it seems that it causes trouble than it solves :|
as now Server B got AD, GC, 5 x FSMOs, and DNS AD, GC, 5 x FSMOs, and DNS already running all of them.
so the remaining steps are:
1. demote Server A
2. reformat it.
3. promote as DC + DNS
4. make it as GC
I found out that having all 5x FSMO roles in one server more convenient as my company only got one domain in a forest.