Most people try to live their lives pretty safely. They wear their seat belts, they lock the doors to their house, they don’t run with scissors.
Yet sometimes these same people don’t practice the same safe behaviors when using their computer. They open email attachments even though they don’t know what the attachment is. They click on links when they don’t know for sure where those links will take them. They search Google for free software and install it without question, even though it very likely contains spyware.
Microsoft has a free download called Steady State. Basically it creates a little “sandbox” for you to play in with your computer. Anything you do while inside Steady State is okay. You can install spyware, get some free waterfall screensavers, click on any link you like, even install viruses. Since all of this activity is happening inside a cache file, it all goes away when the cache file is emptied (simple as doing a restart).
The idea behind this is not to encourage irresponsible computing. One of the practical application is when you have computers that are used by the public, such as in a library or a computer lab. When you have dozens of different people using the same computer each day, there are bound to be some problems created. At the end of the day, you can put the system back to its original state like nothing happened.
You can watch a video demonstration of Steady State, and download it free, here.