Laptop Not Displaying Anything

It seems that, while applying some new thermal paste to my old ASUS K50AB, I somehow messed something up and now it isn't displaying anything anymore.

I took the laptop apart, unscrewed the heatsink and the fan, then went to work removing the old thermal paste with isopropyl alcohol. I applied the new thermal paste without too much issue, then screwed everything back together and tried booting the laptop up. Blank screen, no BIOS or beeps, basically a couple indicator lights and the fans blaring up.

I opened the laptop back up, re-checking any connections I may have messed with, but found nothing out of the ordinary. I reseated the RAM (just in case) and tried booting up again, still nothing. I plugged in an external monitor but still no signal. I checked Google and tried the whole "remove your battery and hold the power button for a minute or two" thing but, unfortunately, still no dice.

One thing to note is that, when trying to remove the heatsink, I actually pulled the entire CPU out of its slot as the little screw wasn't locking it into place for some reason. I put it right back, however, and made sure it was all lined up and secure. (And locked it as well, in order to separate it from the heatsink to apply the new paste.)

Note that this isn't a huge issue since it's basically an old spare laptop, but I'm a little perplexed as to what could have happened. Only thing I can think of is some kind of static discharge that screwed up the graphics display somehow.