On the internet is alot of crap that can ruïn your pc completely. Spyware and Virusses can make a lot of damage. But there is a solution for it.
You can isolate your browser easely with the tool Sandboxie. Some info:
The red arrows indicate changes flowing from a running program into your computer. The box labeled Hard disk (no sandbox) shows changes by a program running normally. The box labeled Hard disk (with sandbox) shows changes by a program running under Sandboxie. The animation illustrates that Sandboxie is able to intercept the changes and isolate them within a sandbox, depicted as a yellow rectangle. It also illustrates that grouping the changes together makes it easy to delete all of them at once.
More info: http://www.sandboxie.com/