MSSQL default instance: how to change regional options ??

[ITGS]

I had upload an asp web application on my VPS with the MSSQL instance installed by default with plesk.

I have some problems with the date format because the msde database engine is in english but I need in Italian.

Alle the pages return the date formatted in english style (MM/DD/YYYY) and create chaos when I insert or update a record using Italian style (DD/MM/YYYY) with ambigous date (ex.: 11/04/2008 that for me is April 11 but for MSDE is November 4).

Is there a way to solve this issue ?
Could I update (or replace) the msde instance with italian version ?

Thanks