Have you tried flashing the BIOS? It's either a button on the motherboard or a jumper that you move to the 'reset' position. Either way, leave it in the reset position for a little while (from 10 seconds to a couple minutes, depends how patient you are) and then put it back to the regular position and boot up again. This resets the motherboard's BIOS to factory defaults and should remove any changes that that floppy drive could have made. If you don't know where the jumper/button is, just look in your manual, or download one online if its available.
Another thing you can do is check the boot order in the BIOS. Its usually under its own tab called "Boot", "Boot order", or something similar. Just move the CD/DVD drive option up to the top so the first thing it does is load from the XP CD. Set it how you want after you're done installing the OS.
