I completely wiped my hard disk on a workstation and now after rebooting, and now it I cannot access a bootable cd, to install Windows 8. What am I missing?
You will need to press f8 or f2 (maybe something else, gigabyte uses del) depending on your motherboard vendor. That will take you into the BIOS menu, then you can change the boot order and set a dvd drive to be first.
This happens sometimes, where if you delete or overwrite the OS, the recovery partition becomes inaccessible. Usually the best thing is just to restore factory default over your current OS without touching it.
I'm not too sure how you get around your current predicament
You need to make sure you get the correct version either 32 bit or 64 bit as needed. The you can run the installation from the dvd you created. There is usually an option to repair the OS which will probably save your files if you didn't wipe the whole drive but only killed the OS. These files are approx. 2GB so be prepared for a wait while downloading.