Noob in need of help: Combining two MKV files

So I backed up my "Phantom of the Paradise" movie, and converted it to an MKV file (not a 1CD though, cause visual quality would suck), and it is encoded as a H264. Anyway, since the outcome was two separate disks, I am wondering if there are any open based software that will combine the two of them?

Thanks.

 

avidemux or mencoder should do nicely

 

Thank you very much friend. I appreciate it!