pc won't boot from any kind of win install cd

[pepperfraggle]

Ok so my sister brought her dell dimension 2400 computer home to me to fix again. Usually about an hour job, but this time, not so much.
I try to boot from the cd (changed boot sequence in bios, then tried making cd-rom the primary master,...) still no luck. Then I add a floppy drive to her dell and try to use a win 98 boot disk and install the cd-rom support and still win xp, win2k, and win 98 install cds cannot boot but I can view the directories of other cds. I even tried a cd-rom drive from another computer. I've never had such a hard time booting from a cd. So then I think, I'll reformat and reinstall xp on the hdd while it's in another dell computer and then move it. Windows xp installed just fine but wouldn't boot in my sister's computer. Only 1.5 years old folks. My first (custom-built) computer finally died after 6 years. Any ideas?
Thanks!

 

[G.]

wow i have a 1.5 year demison 2400 ... set the boot order back to the way it was .. when the memory test is goin on there will be 2 button you can press on will take you to the bios and the other 1 i cant remember what you call it but hit it (youll no what i mean) select cdrom from there

if this dosent work phone dell, where do you live and i get the number?