Good news...The PCR1500 is entirely computer controlled. If your PC is off then it won't work. The IC-R1500 is the version with the control head. If you have a PCR1500 I don't believe the control head can be fitted to it. You may want to contact an Icom dealer to check.
You could alwasy buy a cheap PC, either used or an Asus Eee PC, to run it on.