I went to college for 11 years.
And actually I graduated in 1993 (didn't feeling like posting to correct that) so the drive was pre 1993- and probably pre 1991.
I don't clearly recall events that happened over 20 years ago (tho I can still see the house I bought the drive at- it was on a corner with a bayou behind it).
I was a teetotalar back then but I had cancer in 91-92 and the chemo noticeably affected my brain. These days I'm a social drinker.
But for the nitpickers...
The oldest drive I remember was a 5MB for the apple 2 a friend bought for several hundred dollars. Capacity rapidly doubled after (while price dropped) that so 5-10-20-40-80-used 80 was probably about 6 years after the invention of mass market hard drives.
Per the WIKI
Hard drives had the capacity I remember around 1988 to 1990 so that fits.