MS SQL isn't much different than MySQL. There are slight variances in syntax, but not so much you would notice. Enough though, that you couldn't dump your MySQL db and import it directly into the MS SQL DB.

There are DB converters out there (some free...yikes!) but MS SQL has a built in feature called DTS.

Microsoft DTS is a data manipulation tool that is included with Microsoft SQL Server. DTS is excellent for moving data between various formats and systems such as databases, spreadsheets, and even HTML. The Microsoft Data Transformation Service can be very complex, but most of us will only ever need to use the Import/Export Wizard that is included with DTS.

Using DTS is fairly straightforward, you choose an ODBC data source to read data from, and then select an ODBC data source to convert the data to. You are then given a list of tables to convert, with an option of renaming the destination table and even performing basic transformations on the data before it is inserted into the target database. These transformations are performed using Visual Basic scripting. In addition, you are given control over the table creation statements to be used, allowing you to fine-tune the MySQL table definitions to add parameters such as table handler (InnoDB, BDB, etc) to the script that will be executed.

DTS also has the ability to perform scheduled data transformations, something that can be very useful when you are using MySQL for analysis of SQL Server data or when you just want the latest data available as you work on your application migration.
But for your communication needs... you will probably have to switch from php to asp (again virtually the same, .asp is just "owned" by MS). Unless you use FastCGI or Zend PHP

Again though, if you know php, you can pick up asp fairly easily. Usually just syntax differences. Nothing a Google search won't cure.

In Flash you then just tell it to load or POST or whatever to page.asp instead of page.php.

Now if you need the ASP (know on backend as the .NET) to talk to Flash, then you run into problems. It is difficult but possible. AJAX will be key, or you can try using JavaScript as a bridge between. Or both.

Hope that helps some.

~MoN