I had a huge gap, between playing with the Spectrum in the early eighties to using a PC for the first time around 1992.
I remember using QBasic, and using debug.com to write simple assembly programs - the most memorable one was a simple utility to "undelete" files from MS-DOS, which just involved modifying the FAT.
Most of my memories of the early PC-days were reading Ralph Brown's interrupt list and looking at the source code of viruses, via magazines such as 40HEX.
But computer games as a gateway drug to programming is familiar. I had no idea what the hell EMS (Expanded Memory System) and XMS (Extended Memory System) were. But I managed to get Ultima VII and its apparently bizarre memory manager [0] to work on my computer. I now realize I was clueless about how the Windows OS worked, or basic principles of the command-line, but at least I wasn't afraid of it. Or with editing random INI files. Experimenting with INI files and booting into DOS was the only way to get U7 to run on Windows 95 systems.
[0] http://wiki.ultimacodex.com/wiki/Voodoo_Memory_Manager