might i just add, im running the 7970 on an old dual xeon processor mobo from about 6 years ago which has pci-e 1.0 x16.  

is there a POSSIBILITY that pci-e 1.0's power supply is the reason for not being able to overclock?  i'm sure this isnt the case as the voltages remain the same but could i be on to SOMETHING?

edit

im fairly newbie to all this.  would undervolting the card help in overclocking the memory? is it possible to undervolt the gigabyte i seem to remember reading it isnt.

thanks