Anyone who works on a project on more than one computer has run into a situation where they accidently modified an old obsolete version of their code.
I did that this morning with Darke Dungeon, doing a couple hours work and then remembering that I hadn't extracted the zip file containing my latest updates. With over 30,000 lines of code in 88 files across multiple subfolders, I didn't look forward to checking the modification dates and doing a line by line comparison of the touched files. I wished I had a CVS repository for the thing.
Thank the higher power(s) of your choice for Google. After a page or so of mediocre crippleware I found a real gem in Compare and Merge. It will examine your folders to find which text files have differences. Then you can examine the files side by side with synchronized scroll windows and a color coded bar showing you where the differences are and copy/delete/edit the content of each file. A single drag and drop (or select and click) will transfer changes from one file to the other. It is a truly marvelous piece of shareware with a generous 50 comparisons before you have to register. Frankly if you need to use it more than 50 times, I think you'll find it well worth the price. (I used 10 of my 50 freebies on the Darke Dungeon problem this morning.)
For those of you who don't believe anything is worth the price unless it's free, I also found DiffDaff. This freeware does all the comparisons and difference highlighting with side by side comparisons that Compare and Merge does, but you can't edit the files from within DiffDaff and it doesn't have that oh-so-handy color bar showing you where the diffs are. It's great for freeware (and far better than most of the crippleware I went through before finding it) but those two missing features make Compare and Merge my personal preference.
I welcome reviews of similar packages. I'd love to see if there is anything better than Compare and Merge before I buy the package.