Odd... after a complete reboot it should have removed any "zombie" ArmoryDB processes... So, unless you have some other app/util/service that also happens to be using Port 9001 I'm not sure why ArmoryDB seems to think that port is in use.
Maybe try following the instructions here:
https://veerasundar.com/blog/2009/10/how-to-check-which-application-is-using-which-port/1. Open the command prompt - start » run » cmd or start » All Programs » Accessories » Command Prompt.
2. Type: netstat -aon | findstr "[port_number]". Replace the [port_number] with the actual port number that you want to check and hit enter.
3. If the port is being used by any application, then that application’s detail will be shown. The number, which is shown at the last column of the list, is the PID (process ID) of that application. Make note of this.
4. Type: tasklist | findstr "[PID]". Replace the [PID] with the number from the above step and hit enter.
You’ll be shown the application name that is using your port number.
For example... I know that bitcoin-qt is running on 8332... so,
netstat -aon | findstr "8332" gives:
TCP 127.0.0.1:8332 0.0.0.0:0 LISTENING 15412
and then
tasklist | findstr "15412" gives:
bitcoin-qt.exe 15412 Console 1 331,156 K
Also, my ArmoryDB seems to pick "random" port numbers... do you have 9001 hardcoded in your Armory config file?