Whoa...
Ok that explains it.

You need a BOOTABLE floppy disk in order to flash. It has to have an operating system on it, not just be blank with the flasher...
Make a MS DOS bootdisk and put the flashing programs on it, and away you go. Windows XP can create a bootdisk for you in the formatting options.

But since your computer *DOES* POST, when you put your old CPU back in, why not simply enter BIOS, go to Ez-flash, and flash from there (the flash files should already be on the floppy anyway)? That's what I did when the 2004 modded bios didn't work properly on my computer...