DSP is easier and more straight forward than the CPU. For the CPU, you need to make sure and follow the directions very closely...
Here's what I do:
Plug the USB into the PC.
With the radio off, press and hold the MENU button.
Insert the connector into the side of the radio
The radio should display version info and saying something like "waiting for USB..."
Start EZ Scan and do the CPU update.
Future PSR-900 user...(still hoping!)
PSR-800 x 2 | PSR-500
BCD-396T | BC-296D (voice) | BC-245XLT (mTrunker) | BC-600XLT | BC-IV | VX-8R
Not a Radio Shack fan.....