I have two VPS with Windows Server 2008 and on one I use XAMPP, however server is not so stable and some services do not run as they should. There were also two or three reboots initiated by server itself.
You would need to configure both VPS's to run with IIS 7 and also install/configure real time synchronization (xsync, robocopy, ftp voyager or any other better sync solution).
In addition you would need to configure SmarterMail mail server to run on both servers or at least to configure one server as backup mx.
These two servers will be configured in simple failover system; don't know yet how - with easy dns service or simple failover software.
This shouldn't be a lot of work for experienced programmer active in this field, so please do give me reasonable quotes.