Great question. I have been in two small (<30 employees) companies recently that needed an accounting system. I don't know of any PC based system that is both affordable and good. The current company uses an Access based product called "Yes! I Can run My Own Business". It is extremely well designed from a business point of view, but it has all of the flakiness that people accuse Microsoft products of having. It doesn't actually do anything bad with data, but it sometimes has to be kicked around a bit, restarted and such. but you get all the source code, so you can add, modify and delete features, write your own reports, etc. It has modules for order entry, inventory, purchases, payroll, etc.
All the alternatives I know of cost tens of thousands of dollars.
Good luck.