Micron Home MPC wont boot from cd?

the bios has the option to set the first boot device to cd i did that and saved but it still refuses to boot from a cd. the cd drive runs wild for about 3 seconds than slows so slow u cant hear it or it stopped. the screen this whole time stays black and does nothing. the pc already has a os on it and its working nicely but i wish to upgrade the pc as it needs it badly i found a 400mhz AMD Socket & with 66mhz fsb that will work in the Pentium 200mhz place. but i cannot upgrade because the system will not load windows xp with a totaly diff processor. it had windows 98 and 48mb of ram which i maxed out at 256mb. to put xp on it i had to insert the windows xp cd while windows 98 was up to install but now since im upgrading the processor i need it to start from the cd. the system has no model number anywhere. just say Micron Home MPC on the front. Also where can i find a bios upgrade as this may fix it. if the model goes by the processor then its a Micron Home MPC P200.