hyy1109,
To put Krickles and my comments together....
If you really require IIS:
You need to upgrade to XP Pro (or another OS that will allow IIS)
Then purchase IIS
Then determine what you are going to use SQL Server for and purchase the appropriate version.
As Krickles pointed out...Developer Edition can not be used for a production database. However, it has the same capabilities as Enterprise Edition. So it can be used to design/develop/test a database that you will eventually put on an Enterprise Edition database.
But if you can only use XP Home and upgrade isn't an option, then you will have to use MSDE (Desktop Engine) version and give up IIS.
-SQLBill