在将Ubuntu移植到另一个平台时，如何保存已安装的应用程序?

I'm looking at maybe moving from an older AMD64 to a new Intel dual-core which is 32 bit. Installation isn't a problem but can I transfer all the installed apps? I haven't been able to find anything so far on Google except where the migration is to a similar platform and file-system. I won't change the filesystem but the platform will be different. Is there something on the lines of the "World" file in Gentoo?I'm looking at maybe moving from an older AMD64