If you're trying to download from an MSDN subscription, try contacting the on-line Concierge or some other support channel on MSDN.
Please note, however, that VS 2003 has probably been discontinued from MSDN.
If you don't have an MSDN subscription then I don't believe it's possible to download VSTO at all, except for the "second edition" (VSTO 2005 SE) for creating Add-ins.
VSTO version 2003
Igor_MR
If you're trying to download from an MSDN subscription, try contacting the on-line Concierge or some other support channel on MSDN.
Please note, however, that VS 2003 has probably been discontinued from MSDN.
If you don't have an MSDN subscription then I don't believe it's possible to download VSTO at all, except for the "second edition" (VSTO 2005 SE) for creating Add-ins.