LanSpy

LanSpy is a very easy to use IP scanner that can check a defined IP and retrieve information about the system.
The interface is simple and intuitive, so in case you're okay with the standard settings, you have nothing else to do than to input the IP you wish to scan and start the process.
LanSpy shows information such as logged users, global and local groups, password policy, MAC address, DNS name, TTL and RTT, shared resources, opened files, services and processes, TCP and UDP ports and network statistics.
Of course, you need access to the scanned computer, so LanSpy may fail to retrieve the aforementioned details when scanning certain IPs. Still, the settings screen solves the problem by letting you input an username and password for the scanned system, thus granting access to collect all details.
And speaking of the settings menu, besides authentication, you can also configure the operations to perform when scanning an IP, but also port scanning and the adjacent parameters.
Another good thing about LanSpy is that it can export the results to XML or HTML, which basically allows you to analyze the information at a later date.
Obviously, it needs just a small amount of resources to get the job done and it has absolutely no problem to run on Windows 7, without even asking for administrator privileges to work properly.
All in all, LanSpy may be useful to a handful of users, but without access to the scanned system it is completely useful. Otherwise, it's one of the easiest ways to get info on a specific machine without too much effort.