I'm sorry, but I can't see a quick solution.
Your system isn't complaining because it thinks the CD is too full, but because for some reason it isn't seeing a disc it can write to. If the 'Start' button isn't active it means that Creator hasn't got a 'ready to write' signal back from your CD recorder, and without that signal you're not going anywhere.
I assume that this setup used to write CDs before. Why is this happening now? Check the CD, and the drive connections and optics.
-can your Mac write/read files on the disc? If so, the disc is okay.
-can your PC see the list of files the Mac wrote? If so, connections and read optics are okay.
If it passes those tests but you still can't light up the Start button, I think the writing part of the PC's recorder may have died. To continue you would need to get another old CD drive (from last century, that ECDC4 would recognise) to replace the current drive.
If we get to this point you might consider other ways to get your precious photos off the machine. There's no point trying a USB portable CD or pendrive because Windows 98 won't look at the USB. If your machine has an Ethernet port (rather than a telephone port for dial-up) you could email the photos to yourself. Floppies wouldn't work unless you had another machine to read them in. If all else fails, you may have to get someone to pop the hard drive out and read it with another machine.