taking the rotor guide bolts out and stepping on the gas hard doesn't sound like a very safe idea. it'll probably help, but it doesn't sound safe at all. imagine something 10-15 lbs spinning at a few thousand RPM (the rotor) suddenly flying off.

the PB is a good idea.

it's also possible that his parking brake mechanism has actually slipped off the retaining clips within the rotors. that recently happened to me.

whatever you do, do NOT start banging on those rotors with something like a hammer or the like because you might warp it... unless you plan on buying new rotors. in that case, bang away.

me personally, i just tugged and tugged at the thing and it slowly popped off.

after you get the rotors off and can see the mechanism, make SURE that EVERYTHING is de-rusted and cleaned. the piece on each side connected to the cable that actually pushes the pads apart should be able to bend/rotate in TWO places easily. otherwise, you will have problems.
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Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'