When you install the SQL server, you logined using other windows users, thus, even the current users is administrator, this administrator may not have access right for this folder.
Thus, System will prompted the below error msg when you try to do backup using other windows user account:
Backup failed - You don;t currently have permission to access this folder.
'C:\Program Files\Microsoft SQL Server\MSSQL10_50.QNEBSS\MSSQL\DATA'.
Please grant read permission to your current windows account and try again.
To grant the read permission access right, there is 2 option:
1. Please try to access the data folder in windows explorer e.g. C:\Program Files\Microsoft SQL Server\MSSQL10_50.QNEBSS\MSSQL\DATA , system may prompt you to grant the access right to this folder. after this action, you should be able to do the backup now. However, you may need to do this everytime since this is only a temporary solutions to grant the access right in this folder.
2. Recommended to grant the access right permanently, Pls right click the folder and select "Properties" then grant the access right to this windows user.