I tried the following on the BDP2850 and it works. Was region 2 only, now also plays region 1.
1.- Turn On Philips BDP2800 2.- Press the Home button on the remote. 3.- Press 1389310 on the remote. 4.- Press the power off on the front of the player. 5.- Power on using the front of the player.
Source: http://www.videohelp.com/dvdhacks/philips-bdp2800/11428