Renaming a folder

Hi,
I have a folder called ADSL and inside it there is other folders Routers. So basically under ADSL Folder there is a folder Router and info.xml
 
I wanna rename the adsl folder to adsl1
i did this System.io.directory.move("~/folders/adsl","~/folders/ads1")
 
it gives error access denied :(((( wht shall i do 
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