I'd like to uninstall the preinstalled applications such as the games in Nokia 770 Os2006, since I want more space to install other applications? They are not displayed in the "Show installed applications" in the Application Manager.

Another question, can we install applications in the external mmc card instead of the system card?

Preinstalled applications are not shown in Application Manager by default, because removing one package may cause other packages to be removed too. It is possible to cripple the whole Maemo by removing one unimportant-looking application. You can see all the installed packages if you enable the "Red Pill" mode, though. There are lots of threads in this forum describing how to do that, use the search function.

Installing applications to MMC from Application Manager is not possible. With some Linux skills you could create a workaround for this, for example creating a separate ext2/ext3 partition to your MMC and mounting it to the package installation directory. Or you can run the whole operating system from MMC, as described here: http://maemo.org/community/wiki/HowT..._From_MMC_card