Originally posted by Trolltime:

So the question is i wonder if steam detects any modified data in the game folders. Since i modded NFS heat and i dont know how to turn all the changes back i want to know if the data veryfing does that.

Wrong forum for your question. This is a STEAM related sub-forum, to discuss Ideas and suggestions for valve to make to the steam User Interface on the App, client and website and the online steam services.

But yes Verify will restore all game folder files back to current version, however, it will not remove folders or files added by Mods. It only works on game installed files.

Data verification would do that in 90% of cases.
What verification does is that it compares the files in it's depot with the files on your PC. It will not remove any files you added, but it wioll revert any files that were installed to their installation state.

Basically if you add a file call giggity.ogg to the installation folder, the verification will ignore it.
If the installation created a file giggity.ogg and you deleted it, or changed it. VErficiation would spot the change and redownload giggity.ogg into the game folder thuse recreating what was removed or overwriting the changed version with the original.