prob changing sharing policies via script

Hi
I'm trying to fix the "Logon Failure: The user has not been granted ..." problem when sharing files with windows XP (see other thread in the forum). ? My windows XP being Home Edition, the only solution turns out to be the one using the Windows Server 2003 Resource Kit Tools. The commands I'm supposed to enter from the shell are :
net user guest /active:yes
ntrights +r SeNetworkLogonRight -u Guest
ntrights -r SeDenyNetworkLogonRight -u Guest

Only it doesn't work with me !

the "ntrights +r SeNetworkLogonRight -u Guest" and "ntrights -r SeDenyNetworkLogonRight -u Guest" fail and I get
"***Error*** AddUserRightToAccount -1073741728", which probably doesn't mean much. The result is exactly the same in safe mode, safe mode with network, or normal mode.

This solution should be the right one for XP home edition (allowing to set the policies via the resource kit tool), only if the commands are failing, what else can I do ? More importantly, why do these commands fail ?

Greg