I use Roxio EasyCD creator at home on winxp too. You have to use the "burn CD image" menu option and make sure the "open file" window is looking for .iso images. Also be sure you have set your BIOS (set at bootup time) to the right bootup sequence of devices, ie:
1. Floppy
2. CD-ROM drive
3. Hard Disk drive (IDE)
4. Whatever is left

This should do it if your .iso image is not corrupted (check this with MD5sum)

Moustache