Other than the obvious option of using a more powerful machine (or optimizing your machine for better performance) I'm afraid there's not much that can be done. The encoding, especially of highly compressed video formats like WMV, is just a very computing-intensive process and takes its time. Some codecs will give you a wide variety of encoder settings, some of which can have a bearing on encoding speed. However, most of the time you don't want to sacrifice quality and good compression for shorter encoding times and you end up using the best quality and most computing-intensive settings anyway.