This is covered in the "Philips DVD recorder firmware: upgrades, downgrades..." sticky thread at the top of the Philips sub-forum:
- Switch off the unit at the wall plug.
- On the front panel, hold in the <RECORD> and <EJECT> buttons at the same time, and keeping them held, switch on the power at the wall again. Keep holding the buttons until the disc tray opens.
If this doesn't work, there's a procedure for manual opening of the tray on the HDRW72x, DVDR98x, 7x and 61x:
There should be a small slot on the lower side of the unit near the front and center of the disc assembly. By sliding a small plastic numb from one side to the other unlocks the door so it can maually be opened the rest of the way. You will need a strong, thin object to slide that release nub. A small knife or nail would work. Of course you should follow all safety precaution such as removing power and not damaging anything else.