Keyboard replacement not working.

A friend of mine gave me her laptop to replace the keyboard as a drink had been spilt on it, but the rest of the laptop functioned properly.

The old laptop keyboard still had a few working keys, "e" and "r" notably. When I installed the new keyboard, it didn't function properly either, although this time "e" and "r" did not work, but other keys did such as "l" and "k"!

I have no idea why this would happen, could is be just bad luck at getting a defective keyboard or is the circuity inside the laptop damaged? A USB keyboard works fine, and it doesn't seem like a Windows issue as the keys also do not function when booted into bios.

Any help will be greatly appreciated,

Ross