Hi,
· Why are you trying to extract the file from Windows 7 DVD?
· Which file are you trying to extract?
Some of the files will be locked or in use by the system so you will not be able to replace them while booted to Windows 7. Hence SFC scan tool is used to repair any file corruption in windows 7.
By default design you cannot extract the files. You can copy and paste the file in your hard disk from Windows 7 DVD, refer to the article provided below:
**http://windows.microsoft.com/en-US/windows7/Copy-and-paste-a-file**
Hope this helps,