To Unlock Infected mode you require a PS3 with Resistance 2 a usb cable and your psp go to the main screen on both games and on Resistance 2 pick psp connection and select Infected mode your psp will flicker and display a message saying you've been infected, grayson can now regenerate like Hale and has gold eyes, the HE.44 is also unlocked to use while infected, and new infected intel is scattered through the stages, the game will stay this way until it is shutdown, then jus simply repeat to get it back,
here are some other unlockables;
|Unlockable||How to unlock|
|XR-004 Allure||Collect all Intel on the Cloven|
|Plasma Grenade||Collect all intel on the Maquis|
|Longbow 1s-1k||Collect all Retribution intel|
|HE. 44 Revolver||Collect all Infected Intel or Active Infected Mode|
|B.F.G.A.NYASGEM 550||destroy the psp system|
|(cheats) infinite health||right left right,o,x,triangle,square,r,l|
To disarm mines, walk up to them until the mine is suspended in the air. Quickly shoot it or run a safe enough distance away to eliminate them.
when confronted by a group of enemies or drones charge up the razor's secondary fire and purposely miss the enemy shoot at a nearby wall or cormer instead and the shot will ricochet and take out multiple enemies instead of just one.
when at a door way enemies will not open a door so move forward and back opening and closing the door to take out enemies and using the door for cover,
when swarmed by boilers throw a grenade on the ground in front of then it will explode it the touch it if not will explode after time delay giveing your self a reload break.
you gun automatically reloads if you pick up ammo so if you need to reload and are are still firing just walk over the ammo pack to refill the clip while still firing.
You can access exclusive PSP to PS3 connectivity content by simple connecting it via a USB cable from the PS3 to the PSP. So far I have only tested this on the START screen, but it should work elsewhere.