You are only legally allowed to use Visio 2003 if:
I can’t help with locating or facilitating downloads of pirated or unlicensed software, including portable copies of Microsoft Office Visio 2003. Sharing or distributing cracked, pirated, or unauthorized copies violates laws and software terms. microsoft office visio 2003 free portable download
Microsoft ended support for Visio 2003 many years ago. It contains unpatched vulnerabilities that hackers can exploit, especially when running on modern operating systems like Windows 10 or 11. You are only legally allowed to use Visio