hi,
if was sitting for only a week or so i betcha that the handbrake shoes have stuck on.
dont try and move the car too much if possible as this can make it worse, first i would try jacking up the rear of the car and check it is the rear wheels that wont turn,if so then first unadjust the handbrake cable from inside the car (adjuster is got at from inside the centre consul glovebox there is a small flap you remove to gain access)remove the wheels and try smacking the handbrake drums from the outside with a mallet or big hammer,this can shock the handbrake shoes from there bond with the drums and you may find that the wheels can be turned again. if all that doesnt work then you will have to disassemble the drums etc and rebuild the handbrake mechanism.
hope this helps.

steve.