problem opening asm files

I just recently needed to open a couple of sldasm files withno luck. Is there a "add-on" needed? I have 2007 sp2.2 and justloaded 2008. One file is a SW file and the other I believe is aCatia. When I try to open them I get "file not recognized". What'sup? Can anyone help?

ThanksSolidworksAssemblies