Can't boot xp from disc, help?

I wanna reformat so grabbed an XP.iso and burnt to cd and it works fine on my comp. Changed the boot order in bios. The 'press any key to boot from cd' doesn't appear and windows starts as normal. Checked out http://www.computerhope.com/issues/ch000217.htm#56 and pretty sure none applies. Anyone had same problem and found solution?

>>1
The article covers every possible reason.  Double check your troubleshooting.

thanks hadn't burnt the disc as an image...derp