Click the links I posted above, I put them there for a reason... =\
In fact, allow me to quote myself, if only for vanity's sake:
Follow the steps
listed to find your firmware version. If the version says 3.56, 3.60, 3.61, 3.66, 3.70, 3.73, 4.00, or basically anything above 3.55, you'll need to downgrade, which will require additional hardware on your end to accomplish. For your model, your options for said hardware are: Progskeet, E3, or one of the various dev boards such as the Teensy++ 2.0.
Since it's more than likely you're on the most recent firmware version, or at the very least above 3.55, I've taken the liberty of including a few links below to provide you with some information:
PS3 Dev Wiki - Downgrading Firmware
PS3 Dev Wiki - Hardware Flashing