URLMon.dll is a file used by Windows to help various software programs with their "Object Linking & Embedding" technology
. This basically means that whenever you use the likes of Microsoft Office, and are able to "embed" hyperlinks and images onto your documents - the URLMon.dll file is being used to control that.
The error that urlmon.dll normally causes is this:
"STOP: c0000221 {Bad Image Checksum}
The image urlmon.dll is possibly corrupt. The header checksum does not match the computed checksum"
The error you're seeing is basically caused by the urlmon.dll file either being damaged or unreadable - leading your computer to run much less reliably, and without many of the features which you'd expect. The way to resolve the error is to first ensure that the urlmon.dll file is working correctly on your PC (by replacing it), and then fixing any potentially damaged Windows settings your computer might have (by cleaning out the registry).
The first step to resolving urlmon.dll errors is to first replace the file on your PC with one from the Internet. Not only will this allow your computer to run the file correctly again, but will also prevent a series of other problems from potentially developing. On top of that, it's also recommended that you use a "registry cleaner" program to fix any of the possible errors and issues that your system may have inside. Registry cleaner tools are designed to fix the various damaged system settings that Windows needs to use to run. DLL file errors are often caused by your computer's "registry database" either being damaged or corrupted - leading to all sorts of issues. Registry cleaner programs will scan through your PC and repair the various problems that are inside the registry, allowing Windows to run much smoother again.