I don't remember when or where I first saw a computer, or what kind of computer it was. But I first used a computer at age 7 or 8 in the 1980s, when I took a summer course on BASIC programming.
Here's my first computer, which my dad bought in Aug 1990:
It was custom-built, with 16MHz 80286, 1MB RAM, 40MB hard drive, 1.44MB 3.5" floppy drive, 1.2MB 5.25" floppy drive, monochrome monitor, DOS 3.3 initially (DOS 6 later).
I still have the hard drive, which is almost twice as thick as today's 3.5" hard drives. Back then, "40MB" was really 40MB, rather than 40,000,000 bytes. This drive probably still works although I haven't tested it in a long time.
UPDATE: I see that people are including other "firsts". Here are a few of mine:
First laptop: Dell Inspiron 8200, Aug 2002, with 1.6GHz Pentium 4.
First Thinkpad: IBM Thinkpad 600E, Sep 2002, with 366MHz Pentium II and initially a 6.4GB hard drive, which suddenly died and forced me to splurge $104 on a 30GB replacement drive.
First Lenovo-branded Thinkpad: X60s, Dec 2006, with 1.66GHz L2400 Core Duo.
First touchscreen laptop: Fujitsu Lifebook B-2131, Aug 2006, with 400MHz Celeron.
First netbook: HP Mini 5151, Sep 2010, with 1.66GHz Intel Atom N280.
First 2-in-1 PC: HP Pavilion x2, Dec 2014, with 1.33GHz Atom Z3736F.