Mary,
We currently have a very successful SPC program in our shop. It has taken 3 years to get it where it is today. It took two years to completely change the culture on the shop floor (and that was starting with a pretty good culture). That is where you have to start and that is where it will or won't be successful (The software you use just makes it easier to use the data collected)
We used "Quality starts at the machine" as the mantra to get get culture changed. It takes diligence from the supervisors and buy-in (read $$) from upper management.
Rainbows can help (but don't make it work), Minitab can help (but doesn't make it work), using a software specifically designed for SPC can help (but doesn't make it work). The ONLY thing that makes it work or not is the culture on the floor.
We use: 1. A great shop culture (45 employees on the floor), 2. Formulas in excel will graph output., 3. Quality analysis at the beginning, in-process and at the end.