Hello thanks for choosing Dell. I hope this helps: [URL] page #822  
Hello, I need to reset the admin password for dell Switch S4128T-ON, I have try the instructions on this guide but not working for me.  [URL]  after  modifying the boot it gives me the below errors and can't complete the steps    this SW should be still in warranty, I try to get the Service tag to open a ticket with support but I am not able to find any label  on the SW witch have ST I applicate you help 
reset admin password for S4128T-ON