merge video files?

I need a free program that merges video files, spefically wmv's.
example I have a movie but it is in seprate parts i would liek to join them together as one video file so i can watch it fluently through!

thanks!

and also is there a way to play wmv's through quicktime? or is there a good converter? or a good wmv player besides windows?

thanks i would like the software to be free but if it is not still tell me about it thanks!

thansk so much!