how to set windows service username and password through commandline

This works:

sc.exe config "[servicename]" obj= "[.\username]" password= "[password]"

Where each of the [bracketed] items are replaced with the true arguments. (Keep the quotes, but don't keep the brackets.)

Just keep in mind that:

The spacing in the above example matters. obj= "foo" is correct; obj="foo" is not.
'.' is an alias to the local machine, you can specify a domain there (or your local computer name) if you wish.
Passwords aren't validated until the service is started
Quote your parameters, as above. You can sometimes get by without quotes, but good luck.

windows service command-line

In PowerShell, the "sc" command is an alias for the Set-Content cmdlet. You can workaround this using the following syntax:

sc.exe config Service obj= user password= pass

Specyfying the .exe extension, PowerShell bypasses the alias lookup.

HTH

CodeHunter