what program is used to open .dcx files?

Answer 1

I found a link that may be help you.
http://filext.com/detaillist.php?extdetail=DCX

But if you want to find it for yourself for further studies:
If you are using windows XP>>right click on the file choose open a window will appear asking you to choose either you want to open the file with a program in your computer or you want to search the internet for the program>> choose the second one>>this will take you to the Microsoft knowledge base>>If they have the extension's required info they will answer you else they will give some link that would help you.

If you are using other os(e.g Macintosh) simply go to a search engine>>Type for example .dcx and click on the link that say file extension details for .dcx

Answer 2

Irfan View, its free.

http://www.tucows.com/preview/194967