First computer in the house was an XT with a 20meg hard drive, 300baud modem and a yellow-on-black monochrome monitor. My mum was a journo and used it to file stories from home, very advanced for the time! I used it for typing up assignments and some very primitive games.
First computer of my own was an Amiga 600, although I still mostly used it for assignments and games; I also started messing around with graphics software. Unfortunately I got my Amiga just in time for Amiga to go down the tubes, so it became impractical quite quickly.
First computer I really geeked out with was a 486DX2/66 MMX which I think started with Win 3.11, then went through Win 95 and 98. That was the one that I started hacking around with memory profiles, bat files, 4DOS cli extension, etc... I bought a 14.4k modem to go with it and everything changed from there.