run powershell commands on remote computer

Hi

I have trapsed about the internet looking for a way to run a powershell command on a remote machine but no matter how many varuations i try -no dice

I am trying to use the

invoke-command -computername XP1 -scriptblock{ get-childitem c:\} -credential administrator

I do get the box popup and ask me for the credentials but nothing works

errors: unknown user name or password.  but the password is correct!!

I have set the remotesigning to unrestricted and ran the winrm which gave a positive response. enable-psremoting gave a positive response

any internet articles just keep repeating whatv I have already tried.

Maybe there is some way of defining the domain credentials though I tries all that I know

Any clue??

Thanks

confuseis