How to set format A4 as a default format
If you have set a format letter as a default format on the printer, you can fix it the following way:
Open Devices and printers (Printers and faxes in Windows XP),
choose a desired printer, click on it with right mouse button and choose Printer properties in the menu.
If there is Letter written in the Paper available "window", choose the tab Device Settings
and set format A4 to all trays in the Form To Tray Assignment options.
If you want to have the printer set even better, scroll to Installable Options section,
click on the value Not Installed next to Tray 3
and change it to Installed. Now, scroll back to the top, set format A4 to Tray 3 and format A3 to Tray 2.
You can review new settings on the tab General. To save these new settings, click on the button Apply or OK.