windows cd no booting

[acegik]

I need to load windows again in my computer, but whe I insert the win live cd ubuntu doesn't run it and skips directly to ubuntu boot. I have tryed the cd in other computer runing both OS and it works, but for some reason my pure ubuntu computer doesn't run it. I have tryed changing the bios to boot from cd only and I cannot make the cd boot. Is there any way to do this, delet ubuntu, install windows and ubuntu again? I have backd up my files already. do i need to install MS-DOS? I hope someone know something, I have read several post and apparently you cannot delet ubuntu or reformat the HDD.
My comp Specs are:
Aopen miniPc Duo model mp945-vdr
Intel Core 2 Duo
Thanks!