Information
Auditing access to your shared folders makes it possible to keep track of what's happening; who visits your shared folders, when, doing what. It might not be needed on a "Me and my laptop" networks, although in my opinion it adds a bit to general security of your system and network. When needed, the information is there. Auditing logs are very small files, taking almost no space on hard disk. Auditing does not "eat" the resources of your computer, does not make it slower.
Auditing options can be edited using Windows 7 built-in Group Policy Editor, included in Seven Professional, Ultimate and Enterprise editions. There are also several third party alternatives, for instance ShareAlarmPro. This tutorial is however about how to do it with gpedit.
