I've been developing my site on XAMPP, and i put a Amazon EC2 windows instance with xampp pre installed to host my site on AWS, but XAMPP is bad right? it's meant for devoloping? Should i use anything diffirent? I want use windows, i run php & mysql, I would like to have phpmyadmin also.
Well, basically, you have two paths; use Windows or use Linux. I'm biased, but I'd really go and use Linux. Running Windows is most certainly going to be more expensive (Windows licenses have a cost), and, in my opinion, although PHP runs on Windows, it's more at home at Linux.
If you use Linux, things are much simpler. Choose a distro and use the distro's packages for PHP, Apache, MySQL, etc. They will work out of the box, receive security upgrades easily, etc.
If you want to use Windows, things are a bit more difficult. For starters, you might want to consider using IIS, which is Windows' official web server. I don't really know if IIS+PHP is really "better" than Apache+PHP on Windows, but I suspect so- and Apache's pretty UNIXy, so probably IIS "fits better".
On Windows, there's no "official" packaging of PHP, MySQL et al. as there's on Linux distros, so there's choices to be made, basically using the software from the original source or use a distribution such as XAMPP.
You have to balance effort (probably distributions require less work), timely updates (which are vital for Internet publicly facing services- probably original packages have advantages here) and quality (can't really tell).
It would be much cheaper and ( in the long run ) easier for you to run PHP / MySQL on a Linux shared hosting or Virtual Private Server. Linode is particularly cheap and relatively reliable. Both Linode and Slicehost ( owned by Rackspace ) have great documentation on how to get this running:
If you intend to host Web Applications using open source software, the path of least resistance is to host on an open-source stack, meaning LAMP in your case.