A sandbox is a security mechanism for separating running programs. It is often used to execute untested code, or untrusted programs from unverified third-parties, suppliers, untrusted users and untrusted websites. – wiki
There is a great program for Windows named Sandboxie. Sandboxie runs your programs in an isolated space which prevents them from making permanent changes to other programs and data in your computer. You can download it from here.
After Installing Sandboxie right click on any executable file or archive and choose Run Sandboxed. Click OK on the popup window.
Now you can easily run/test programs without worrying about viruses and other malware.