My dell laptop keyboard only works half of the time. WHY?

My dell laptop keyboard keys only works half of the time. I spilled liquid on the keyboard a couple of years ago and since then I have replaced the keyboard part on my laptop and it worked for awhile but now I have to plug my desktop keyboard into the usb port and some of the keys on that work and some on the laptop. This does not make any sense to me. Any ideas of how I can easily fix this or why this does this?? Thanks so much!