consolidate two data files

How can I combine two data files (i.e .mdf and .ndf). We had two data file in our old server due to disk limitation. In the new server we don't have such limitation so we like to consolidate the two file in one. What is the best way to accomplish that?
ThanksFollow this:
http://groups.google.com.au/group/microsoft.public.sqlserver.server/browse_thread/thread/d7fa8af9c5ca5ca/71636c29fdf2666c%2371636c29fdf2666csqlsql