Probably one of the Quakes, if I remember correctly. I think that must be it because I remember getting the Quad power or whatever it's called. My Dad would let me play games with him on his computer. He probably did most of the work, until I could do it on my own. Prince of Persia was also there, at some point.
I was born in 1990 so most of my memories aren't of the classic old school games, but there you go.