Why is my Ubuntu 10.10 CD not booting?
Solution 1:
If you boot your computer with... anything bootable, and then you insert the 10.10 CD you burned, is it recognized and mounted (i.e. is it readable)?
If not, and you have an Ubuntu distro running, you can test with wodim -atip and wodim -toc (they are in Ubuntu package wodim, the old cdrecord) whether the CD media is recognized as writable and if there are tracks.
If it is recognized, there is another package that can help you, cdck: it can tell you what's the content of that CD and if it's bootable. E.g. with a Knoppix CD that I burned myself I get:
Try to find out what sort of CD this is...
CD-ROM with iso9660 fs
iso9660: 688 MB size, label 'KNOPPIX'
Creating software: 'KNOPPIX'
bootable CD
This won't probably answer to your question 'why', but it should help you track where is the cause of the problem.
Solution 2:
As Allan suggests, some more info would be helpful, but I'll post some suggestions here, as I can't "comment" at the moment.
Have you definitely set the CD drive higher than the HDD in the BIOS boot settings?
Can you boot a different CD?
If the CD is booting, but crashing with some form of kernel panic, you can try the various options in the CD menu (like
ACPI=off, which is needed on some models of laptop, such as the Toshiba Satellite)
Solution 3:
one of the possible problem is if the file is not downloaded properly. The easy check is to calculate sha or md5 checksum and compare it with the original placed on the site you downloaded from.
the other problem can be if you burnt the ISO as a file not as an image