Select any file you want, right click it and select properties.
Under the General tab click the ‘Advanced’ box.
Uncheck the option for file compression.
Click OK and then Apply. a page will appear giving you the option to apply this change to just this folder or to all folders, select all to turn off global compression.
Having done this the computer will set about the task of uncompressing all the currently compressed folders again, it will take some time to do and a progress bar is displayed to let you know how things are going, but still expect a wait for it to complete.
Other than this the best way to compress files is to use Zip files, gives a far better compression ration than the NTFS version and is less susceptible to corruption during transfer or copy functions.