Trouble converting file formats

[convert]

I am trying to convert .mov files to .wmv files. Sometimes it works. But usually, all it does is create the destination file. Then, the program either crashes and closes immediately, or it seems to be doing something for a while, then quits. Either way, the destination file is empty. I don't know why it sometimes works OK. I have version 2.1.3 of VLC. I tried a later version, but it locked up my (somewhat old) computer when I tried to use it.

I found no help in FAQ or troubleshooting tips. Forum subject titles are often so uninformative, it's hard to search them. I am a complete novice here. Any tips would be appreciated.