Rectangular black box with red digits flashing on top left of screen.

[Bluejax878]

Hello I've started up my computer today and noticed that there is a black box with red digits that looks as some sort of timer that keeps on flashing. What is it and how can I get rid of it? Thank you

 

[Colif]

is it on desktop or shows up as soon as you start?
if at startup, is your PC home made or brand name? if home made, what motherboard? if brand name, what make/model?

If at desktop, run av & malware scans as a precaution (what i do if anything weird happens on my PC)
check the start up tab in task manager and see if anything strange there
check in the area of task bar that is normally hidden (click the up arrow) and see if anything strange running there
did you install anything new recently?
do digits look like temperatures or something else? a screen shot would help (upload to imgur and share link here)