Crystal Security is a cloud-based application which detects and removes malware from your PC.
The program arrives as a single executable, impressively, with no installation required. Launch it, run a "Quick Checkup" and Crystal Security crawls your PC, looking for suspect files.
Anything dubious is submitted to VirusTotal and Crystal's own cloud system, you'll be warned of positive results, and get a chance to allow or remove the file.
That's not all: Crystal also provides real-time security, detecting new files as they arrive on your PC (downloads, program installations), and again checking them for threats.
If you're happy with your existing antivirus and don't need more real-time protection, Crystal's monitoring can either be disabled or simply tweaked to suit your needs. You might turn off file scanning, for instance, and have it just watch running processes and autorun locations, giving you some extra security with minimum impact on system performance.
Improved: Dynamic engine.
Crystal Security is an interesting antimalware tool, plenty of features and very configurable, but the total lack of documentation will leave beginners bewildered. You'll need some security expertise and quite a bit of time to get the most out of the program.