Xbox 360 will not update

[gmcfa]

Hello guys,

I have an Xbox 360 that will not update. The console comes on ok then I get a screen saying cannot find update disk press A to continue.

then I get a breif update logo/animation then it goes on to a screen saying contact xbox support webpage with 2 codes:

PV: 2.0.8498.0 CV: 2.0.8955.0

I have tried following the advice on the site tried both methods of writing the update to disk and to usb stick but both fail.

Is there any way I can reset the whole process and update a fresh?

Thank you.