If I remember correctly, the Sony A5xx series have a form of built in HDR, so I would assume it is in the A450 too. It doesn't go the more extreme versions of HDR though. Even if not, you can take images with it suitable for further HDR processing.
PSP7 is rather ancient (I still use it too!), and doesn't have any specific HDR capabilities in it.
See this thread
on HDR if you haven't already.
Personally I have Dynamic Photo HDR
as the most easy to use one. Photomatrix
is also a popular option, as is the capability in Photoshop CS5. All have demo versions for download so you can have a play.