While I was performing some extensive WordPress plugin compatibility testing, I was getting frustrated with having to wait for what seemed like an eternity for page refreshes to occur. I did a little Google-ing and found an excellent open-source software package called XAMPP that runs on Windows.
It lets you run Apache (a web server program), PHP5 (a server programming language), MySql (a database program), FileZilla (an FTP program), and Mercury (an e-mail server program) on your local hard drive running a 32-bit version of Windows. You can manually start the programs/servers or run them as installed services. Here is a good XAMPP installation tutorial.
The XAMPP program lets you install a test blog locally on your hard drive, which greatly speeds up development and testing.
If you have a shared web hosting plan and you have ever seen a Server Error 500 message as a result of activating a plugin or accessing some part of your blog, you may already know that shared web hosting plans don't typically include access to the server error logs. The main advantage to using XAMPP is the ability to access your own, local server logs directly to perform server-side scripting language troubleshooting. Once you have tested and verified your site, you can then upload it to the live host on the Internet, without any interruptions in site availability.