To change the whole system language you have to install new service pack with different language. Example: if you have XP SP2 in Eng and want to have it in Italian then you will have to download SP3 in Italian and change some registry keys (Go to HKEY_LOCAL_MACHINESYSTEMControlSet001ControlNlsLangua...

Yes, it is included in it but at time I have no specific idea about it. You can check the available documentation. It may be you can get idea about it.

You can try this :
Start deluge from the Command Line and watch for error messages. Post complete output and If necessary, start deluge in verbose mode.
~]$ deluge -L debug -l ~/deluge.log
For details:
~]$ deluge --help