The c1.dll error stems from the Microsoft Corporation. Therefore, it should be a perfectly safe and legitimate DLL error. Of course, the only way to know for sure if it is a virus or a legitimate error is to run a registry scan. ZookaWare PC Cleaner offers a free registry scan.
You can download ZookaWare PC Cleaner free, and it will scan to see if it poses a real threat. I do want to offer a word of warning. Some less reputable companies offer free scans, and then show false positives, so you will buy their product. ZookaWare, the makers of Regzooka, is a member of the Better Business Bureau and also offers a 60-day money-back guarantee.