If you find the file c3.dll on your computer, you need to immediately run your antivirus software, as this file is commonly found hiding the Haxdoor virus. Dynamic link library (dll) files contain bits of code, and while this dll file itself apparently is not dangerous on its own, it is usually found as part of the virus. Running your antivirus software is the only way to be certain that this is not part of that virus.
You may also want to run a check for spyware, and we recommend running a free SpyZooka scan to check your system with no strings attached. If you find that your computer has viruses or spyware and want to figure out why you are getting an error with this file, try running a free ZookaWare PC Cleaner scan.
ZookaWare PC Cleaner checks your registry for errors. Registry errors are the most common cause of dll file errors that you see. Running ZookaWare PC Cleaner will find any problems in your registry so you can see what sort of issues may be happening and solve them. Remember to regularly run your antivirus software, and keep your registry clean by running ZookaWare PC Cleaner as well.