Oh man, my fondest early memories with computers was modifying the autoexec.bat and config.sys files so I could play DOS games. I can only describe the feeling of finally figuring it out and getting a certain game to work as pure joy.

Conversely, the feeling when I changed something incorrectly (without backups of the original file, of course) and the system error'd out during boot - sheer panic.

did you load himem.sys? how about emm386.exe? does your sound card have an OPL3 or the OPL4 MIDI chip? Does your trident VESA card on the ISA slot have 1MB VRAM? stacker, drivespace or doublespace? choices! I just bought me a Seagate medalist 1-Gigabyte hard drive. Should I make it a master or a slave on the ATA bus? Make sure the Turbo button is pressed, if Doom is slow to load!

QEMM! Protected Mode! Unreal Mode! TSR! Ralph Brown's Interrupt List! Oh man!

Had so much with my friends while in high-school trying to figure out what kind of weird graphics mode this cool game called "Scorched Earth" used... It wasn't 320x200 :)

Of course if it was on IRQ 12 half of the games wouldn't work (long story, and yes, due to another x86 quirk)

dos4gw.exe http://en.wikipedia.org/wiki/DOS/4G

univbe http://en.wikipedia.org/wiki/UniVBE

oh my!