Have you tried Windows Marketplace client yet? No? Don’t have a 6.5 ROM update or device yet? No problem. Download Windows Mobile 6.5 standalone emulator images. These come with a fully functional Marketplace client you can download and install apps with. The Windows Marketplace for Mobile client provides users a streamlined experience to purchase and install applications on their Windows Mobile 6.5 devices (coming soon for 6.1, and 6.0). As you’ll notice when installing applications, user interface’s different from typical CAB file installation (see on left) perhaps you’re used to. It’s very important that Marketplace install experience be uniform and streamlined. To keep it this way, no custom UI (errors, prompts, informational messages, etc.) should be displayed during installation or uninstallation. If you absolutely must display custom UI, there’re some things you should know about Marketplace client.
Full Article: Windows blog