How to change a ubuntu 9.04 i386os to a ubuntu 9.04 amd64os?

"I have since upgraded to 9.04. I have burned a copy of ubuntu 9.04 amd64 variant, which is more appropriate for my computer and have tried to implement it but synaptic responds that it does not find any packages in the burned copy"

You need a new install, not an upgrade. If the copy you have burnt is good just boot off that.

http://www.ubuntu.com/getubuntu/download

https://help.ubuntu.com/community/BurningIsoHowto

Ok try booting up from the cd and hopefully you should get to a menu with "Try Ubuntu without changes to the machine". Choosing this option should get you to a working desktop, which we call a "LiveCd session", if it works. Here's a guide if you have trouble getting to that first menu
https://help.ubuntu.com/community/BootFromCD

If the LiveCd session works then you should be able to surf the internet into here directly from firefox on the top taskbar, it should pick-up on your internet connection :) Then just use the icon in the top left-hand corner to install Ubuntu in the proper dual-boot way so that you can keep popping back into 'old' Ubuntu at least until you've got used to doing everything in the new one.
https://help.ubuntu.com/community/WindowsDualBoot
I know this guide is written for dual-booting with Windows but it should be easily possible to set up a dual-boot between 'old' and 'new' ubuntu, thus making sure that you can shift across gradually as the 64bit version uses different version (ie 64bit versions) of most of the programs you are already used to using so tweaking all the settings to what you have gradually setup over the years might take a little while ;)

Good luck and regards from
Tom :)