Passcode required upon startup directly after Asus logo?

So this one is kindof a difficult story. My laptop had gotten stolen and sold by roommates at the time. It was MIA for approximately 3 months. During this time, I had tried to lock my computer via microsoft account but seeing as they didn't have the charger, and apparently there wasnt any Wi-Fi, i wasnt successful in locking my computer to my knowledge. Long story short, I located my laptop and was able to retrieve it. As I thought, the battery was dead, so when I plug it in and turn it on, the following happens: I press the power button, the green power light turns on, the screen shows the ASUS logo for about 1 second, then the screen goes to a black screen with a password bar and the words enter password above it. I tried all the passwords I wouldve used or have used, but have not been successful. I'm very frustrated and would just like to be able to use my laptop again. Anyone have any suggestions or thoughts on what I might be able to do to fix this?