The Aspire One 721 comes equipped with a keyboard that has international language support. Those specific letters if you look have a blue function below them as well, or should if it looks like our unit. The function of those keys could have been reveresed depending on the keyboard layout you are using.
I would like you to check your keyboard language. On the taskbar there should be a language bar that you can click and choose the different available keyboard layouts. Select the appropriate language and this should resolve your issue. If this is not available, use the following steps in Windows 7:
Open the Control Panel, select Region and Language, then click on the Keyboards and Languages tab.
From there click Change keyboards, then check what language you have selected.
Select the English keyboard if necessary, then click Apply then Ok.