In dos, is there a way to merge a set of files so that for instance
Just like the paste command on *nix systems
Nope, you'll need to merge the lines with a program, or a scripting language, like Python.
Update: Look at these Win ports of GNU utilities, it includes paste (.exe)
If the data reasonably simple, you could do it with Excel. Or you could download OpenOffice and do it in Calc, but the method in Calc is a pain. (You need to paste the data into two columns then merge them with the "Concatenate" function, in formula form (e.g. concatenate(Row1; row2;))
Definitely agree that a port of Unix tools or a scripting language is the way to go (although VBScript or Powershell are probably more convenient choices than Python for Windows users), but merging two files IS possible in DOS:-
File under "Just because you can, doesn't mean you should." :-)