Can't restore

I tried to do a restore and got the following :-
System.IO.IOException: Access to the path ‘G:\G300_email’ is denied.
   at System.IO.Directory.InternalMove(String sourceDirName, String destDirName, Boolean checkHost)
   at DbBackup.FormBackup.Restore(String backupFile, CancellationToken cancellationToken)
   at DbBackup.FormBackup.Restore(CancellationToken cancellationToken)
   at DbBackup.FormBackup.<mainform_load>b__27_0(Object a, DoWorkEventArgs b)
at System.ComponentModel.BackgroundWorker.OnDoWork(DoWorkEventArgs e)
at System.ComponentModel.BackgroundWorker.WorkerThreadStart(Object argument)</mainform_load>