An attempt to attach an auto-named database for file C:AppDataaspnetdb.mdf failed

An attempt to attach an auto-named database for file C:\User\Administrator\WebSites\project\App_Data\aspnetdb.mdf failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share.

I have to connect database... database with the same name has not any duplicate copy. but on every attempt of conncetivity above error occurs.... How this error be removed???

Thanks in advance