Associated .IPA software

Windows
IPA file extension
iPod/iPhone Application File
Files with the extension .IPA are application files used by Apple devices such as the iPod and the iPhone.
.IPA files are essentially zipped/compressed archive files utilising an Apple specific file extension, by changing the extension to .ZIP and unzipping in a program such as WinZip - some idea of the files contents can be gained.
zip -9 -y -r MyApp.ipa Payload/
I saw someone said that you can change the extension to .zip and view that way through WinRAR but that wont work. Any ideas? Is there a program I can use?