MS has been going for 35 years - longer than many of us (but not me, ahem).
My first recollection was using DOS, probably DOS 3 (It was a long time ago). I can distinctly remember getting very excited when I upgraded my PC (8088 to 8086?) and couldn't believe how much quicker the dir scrolling went by - Jeepers - my eyes could hardly keep up!
But then again my first proper PC was an ATARI ST which pre-dated the above (at least for me) and I remember a very buggy version of 'Microsoft Write', which I still have (will dig out for a photo - stand by).
(Found it with along with my copy of DBASE II and Atari ST "Starglider" !)