For simple stress testing, my favoriate tools are JMeter and Microsoft Web Application Stress Tool. JMeter is more comprehensive but requires a little bit of setup. Microsoft Web Application Stress Tool is a old tool from Microsoft and is not actively mantinaed, but it is super simple to use.
You can still download the tool form here. I am trying to intall it in Windows 7, but I run into some problems. It is complaining that MSVCP50.dll is missing. I managed to find the DLL from here. It even comes with the steps for installation.
To be safe, I didn't add it to the windows system folder. I just added the dll to the installation folder and run the registration of the dll:
It shows some warnning message, but just ignore it.
Re-install Microsoft Web Application Stress Tool again and you are ready for your stress test!