In Windows XP, you'll find a very handy tool called, the System Information Tool. The main purpose of this tool is to help in troubleshooting computer issues. As an example, if you are having a problem with an optical drive, you can use this tool to identify the status of the driver for this drive. While the troubleshooting aspect of this tool is used by the more advanced users, this tool is handy for all users who wish to find out information about what is installed on your Windows application at a glance. Here's how to start the System Information Tool:

Go to Start>> All Programs>> Accessories>> System Tools>> System Information.

OR - Go to Start>> Run. Type in: msinfo32.exe [Enter] or click OK.

The categories of information you can expect to find in this tool are:
Installed Components
Hardware Resources
Installed Applications
Software Environment
Internet Explorer