The first PC I owned was an Atari 800 - and boy was I impressed with all I could do in basic! I must have made a dozen choose your own adventures by the end of the first week
The first PC I ever used (many years earlier) was the commodore PET (our school received one as a gift), which I believe was the predecessor to the C64.
I do remember the Sinclair as well, mostly being frustrated by it
