*might* still work actually; the database itself is just a file, and you don't necessarily need the MSAccess application once the file is created, if you have another app (such as asp.net or even php) that can insert and retrieve data from said file.
Never tried it though on x10 honestly - it's worth a shot
Yes. You already have all the tools you need if you are running entirely under Windows 9x/Me, or NT/2000, where you can use ODBC and Microsoft's ODBC drivers for Microsoft Access databases.
If you are running PHP on a Unix box and want to talk to MS Access on a Windows box you will need Unix ODBC drivers.