Sandboxie

Product: Sandboxie
Author: Ronen Tzur
Website: www.sandboxie.com
Type: Free
Requirements: Windows XP/Vista/7

Tired of dealing with rogue software, spyware and malware?
Spent too many hours removing unsolicited software?
Worried about clicking unfamiliar Web links?

Sandboxie runs your programs in an isolated space which prevents them from making permanent changes to other programs and data in your computer.