My first HD was a 3.5" Conner 540mb drive which I managed to cram inside my old Amiga 1200! The keyboard bulged slightly and I had to use an old A500 PSU to power the system as the A1200 actually had lower output, but it made workbench usable!
Woo, I remember the first computer I had... An old Pentium 2 Dell Optiplex Desktop lol. Beige, big, ugly, loved it. Hard drive, not sure...Maybe 5gb?
1st PC in 1992, an AMD 386DX40 system with MS-DOS (no Windows at all) - 40MB HD later upgraded to a 120MB then a 500MB!