Panda Cloud Cleaner, or cCloud as it's more commonly known, is basically a stripped-down version of Panda's full featured antivirus scanner. It doesn't have nearly the number or variety of features that other spyware detectors have, but it's still a very good program and can help protect your PC from many different threats. It's been developed by a group called the Panda Rogue Team, who released it in order to make money through advertisements on your PC. Although many people have found it easy to use, others say that it causes way too many problems for their systems.
The main problem with this antivirus software is that it's actually designed to scare you into purchasing the upgrade to the full version which then also brings along some unknown threats that aren't included in the free scan. The way that the clouds program works is that you're prompted to scan your system for a bunch of different threats - it wants you to buy the upgrade because it says that all threats are detected and that if you don't, they will cause a lot of damage. The problem is that the "panda security suite" isn't actually full coverage of all the threats that your computer could be exposed to, and as a result you might end up getting caught with a series of different threats that your system is not prepared for. This is one of the biggest problems with this particular free software...
The problem is that it's not like most antivirus scan programs at all. Many of the ones that claim to be able to find all malware and viruses have several components that work together to detect threats. While they might find the virus, they'll also scan for missing files and missing settings - both components that will cause problems for your system. As a result, your system could be damaged even further and you could end up with a whole lot of problems that might be impossible to fix, if you used the free scan. However, air has a great security suite that protects against the most threats, and that means that your scanning results will always be accurate. And since it's paid, you can feel secure in the knowledge that your system will be kept safe.