Anyone know of a good, easy one ?  Also, Free would be a bonus too.
 :-D
There goes my lurk tag.
Most of the MSI packagers suck.  
My preference goes to any manager that can take a before/after snapshot and create an MSI of the difference.  I find they are the easiest to use.  The problem is that easy costs money. 
I use 
WinINSTALL at work.  It's probably one of the better ones out there but you would expect better from a program which is horrendously expensive.  There is an evaluation version that will allow you to build and edit non-crippled MSI files.  If you are looking at doing a quick or one off MSI it might be worth the download.  WinINSTALL LE used to ship for free with Windows 2000 Server so you *might* be able to find a version out there.  I'm pretty sure the LE never did before/after snapshots though.  It's been a while since I used LE; It may not allow you to edit the MSI package.  If you get that far you will find out pretty quickly.
You might want to take a look at 
MakeMSI as well.  Warning: Colour scheme is awful.  He has some decent documentation on there and it may be what you are looking for.
If your program is simple enough (ie: only registry/.ini changes), just get a snapshot program (InCTRL comes to mind) and build a .reg file with your changes and avoid the mess that is Orca.
Edit: apparently the forum code auto-attaches http://