wmv to avi files

How do I correctly change wmv files into avi files? I have down loaded a lot of software and none of them seem to work. Can some one please explain the process step by step please. Ive been tring to convert these files for days and I still cant figure it out. I have down loaded winavi, and I cant understand what it wants me to do. WinAvi is on my desktop and I cant do anything with the software. It keeps saying"Unable to read the dictionary of the application or extension because it is not scriptable." What does that mean? Should I download another softwear? Help please. Thanks

 

Can Anybody Help Me?????

 

Moving to Langjökull in Iceland - so all the info I posted is moving with me!

 

If you don't use Windows OS,maybe winavi can't work.
one way,install the Windows OS
another way,look for other software which can work for you

 

I dont have windows OS. Is that the problem? Should I download it? I am on a mac. Is it possible to download windows on a mac?

 

Yes,WinAVI only work with Windows.
I haven't try to install that,so i don't know,may be you can try.