Did you drag or copy the files from a disc? That almost always changes the attributes to read only. I've found that clicking a folder to change it's attributes doesn't help. You need to get to each file.
Open the folder, click on the first file, scroll to the bottom, hold shift and click on the last file to select all the files within the folder (but don't select any sub-folders, you'll have to repeate this process for each of them), right click, click properties and unclick read-only. Click OK. Your files should now all be writeable.
I recently dragged a whole bunch of files off a disc and getting them back out of read-only mode one folder at a time was a b****.