That's the correct idea. Things that can go wrong:
1. BIOS setup isn't set to boot from DVD first.
2. DVD isn't bootable (you didn't make it the correct way)
3. DVD-drive isn't fully functional and needs replacement.
You say that 1 has been taken care of. That leaves 2 and 3. Both are easy to check with another bootable DVD and another PC.
we downloaded the Windows 7 release candidate and it wont do a clean install on top of the Windows 7 Beta.
We are running a Gigabyte Motherboad (GA-MA770-DS3), AMD X2 Athlon 64-bit processor (AM2 Athlon X2), 4GB Kingston RAM (Dual Channel DDR2 1066Mhz), Seagate 500MB harddrive (Seagate Barracuda 7200.11 500GB 7200RPM SATA II), Sony DVD Writer (AD7200 SOBINT20X DVD Burner), video card (ASUS 9400GT Silent 512MB).
I believe we need to do a "clean install", which I understand to mean backup all personal data somewhere other than your harddrive, then put the DVD containing the ISO image into the DVD drive, select Boot from CD/DVD only in BIOS and reboot.
After doing that the PC boots up with the existing Windows 7 Beta (Build 7000) OS installed and seems to ignore the ISO image on DVD. We have unplugged everything from the PC except the keyboard, power supply and monitor and the problem remains. We have also downloaded the Release Candidate twice.
Any hints? Thanks,