ComputerBlog

​My first thought is to modify the Content Type named Folder, but it is "sealed". (Microsoft locked the door!) So I created a new Content Type based on Folder, added the custom column, added the content type to the library and magically I found my custom folder type in the New dropdown. Here's the steps:

1. Go to Site Actions, Site Settings 
2. Click Site Content Types 
3. Click Create
4. Give the new content type a name such as "Enhanced Folder" or "Product Spec Folder"
5. Set the parent content type group as Folder Content Types
6. Set the parent content type to Folder
7. Add the new content type to a Group. I put it back in the "Folder Content Types" group
8. Click OK
9. Scroll down to the columns section and click Add from new site column
10. Name the column and set all the usual column options
11. Repeat for any additional columns (Release Date, etc)
12. Click OK
13. Go to your document library
14. Click Settings and Library Settings, or in 2010 click the Library ribbon tab and then click Library Settings
15. Click Advanced and set Allow management of content types to Yes and click OK (this may already selected)
16. Scroll down to Content Types and click Add from existing site content types and add your new folder content type
17. Go to your document library and click the New dropdown, or the New button in the 2010 Document ribbon, and add your new folder!
18. Go to the View dropdown and click Modify this view and add your new folder meta data columns (you will probably want to move them to just after the Name column)​