PC DOS and all that
My first experience with an IBM PC was where I worked, my department got the company PC one day a week. I made sure I became the department's expert on that.
Its first upgrade was a full size 5.25" floppy drive. Woo hoo. I think that drive was equivalent to about a month of my wages.
I've still got (somewhere hopefully) PC DOS 1 (or maybe 1.1 ? ) on floppy.