Postgre will be a better option than MySQL if you're leaving MS SQL.
Hate to rain on your parade but,
• SQL Server 2000 Enterprise Edition and Standard Edition run on Microsoft Windows® 2000 Server, Windows 2000 Advanced Server, Windows 2000 Datacenter Server operating systems, Microsoft Windows NT® Server version 4.0 Service Pack 5 (SP5) or later, and Windows NT Server 4.0 Enterprise Edition with SP5 or later
• SQL Server 2000 trial software and SQL Server 2000 Developer Edition run on the operating systems listed above for the Enterprise and Standard Editions as well as on Windows XP Professional, Windows XP Home Edition, Windows 2000 Professional and Windows NT Workstation 4.0 with SP5 or later.
• SQL Server 2000 Personal Edition¹ and SQL Server 2000 Desktop Engine run on the operating systems listed above for Enterprise and Standard Editions, as well as on Windows 98, Windows Millennium Edition (Windows Me), Windows XP Professional, Windows XP Home Edition, Windows 2000 Professional, and Windows NT Workstation 4.0 with SP5 or later.
Doesn't show any unix on the list. That means any unix webhosting would need a windows server just to run your SQL server. Not very economical huh? I'd stick with an open source dbase.
Saludos
Gerardo