Remove duplicate entity from a column

Select the column by clicking top of the column, then go to data-validation, select custom and type the

custom rule =COUNTIF(A:A,A1)=1

Access Denied error in Windows 8

after long time posting again..

I moved to windows 8,have some files from windows xp,now can not access them,access denied error

Here is how to take ownership of those files in windows 8(gui method did not work surprisingly)

a) Press “Windows Key + Q” to open Charms Bar.
b) Type “cmd” without quotes in the search box.
c) On the left pane, right click on the “cmd” option and select “Run as Administrator”.
d) Type "TAKEOWN /F c:\windows\winsxs /A /R" without quotes press enter. 
Note: Here c:\windows\winsxs is the file location. 
e) Type “ICACLS c:\windows\winsxs /grant:r Everyone:F /T” without quotes and press enter. 
Note: Here c:\windows\winsxs is the file location

Now even after doing that and even after getting the success of the commands I was still getting  the access denied,so I tried to to take ownership of the whole folder and enabled inheritance and it worked unlike before.

Here is the the link that helped me.

http://answers.microsoft.com/en-us/windows/forum/windows_8-security/you-do-not-have-permission-to-view-this-objects/5939dbf4-ca81-4f14-b455-ede115af924e