I was reminiscing on my computer experiences on my drive home from taking my A+ exam.
I don't recall the very first PC problem I fixed. I just remember my dad bringing home a 286 machine from work and it not operating. I don't believe it booted anything at all. Maybe it was summer, because I asked if I could play with it when he went to work. He said, "If I can't fix it, you can't, but you can mess with it." When my dad got home from work, the machine was at an MS-DOS prompt. :)
The first hardware issue I recall was much later. While living at my grandparents with my mother during a separation from my dad, I kept my awesome 486/66MHz (this is different from the separation which left me without a PC at all -- where I used the Commodore 64 to get on dial-up). Linux was gaining popularity. I probably noticed before that I had issues with my floppy drive, but I rarely used it. To boot into Linux, the floppy drive was a must have! I wrote a boot floppy just fine, I think, but it'd only boot once out of what seemed like a hundred tries. I'd slam eject, forcefully slap the disk back in, and hit reset on the PC over and over..
Linux eventually booted, but this had to be looked into because I was going to keep experimenting with it. I lugged the CRT to the floor, opened up the case and began poking around. At the time, CPUs did not have a fan. I don't recall mine even having a heatsink. I do believe they started using Zero Insertion Force (ZIF) sockets at this time, but maybe my mainboard did not. My video card was very long, using a VLB expansion slot, and sat fairly close to the CPU. This slot stretched from one edge of the mainboard to the other.
So firstly of course I checked the floppy ribbon cable. Made sure it was tight and clean and gave it a test run. That did not fix it. It probably took me some time of easter egging to reseat EVERYTHING. It turned out, the large VLB video card somewhat warped the mainboard, which left some pins of the CPU from seating well. I suppose I reseated the video card, then the CPU afterwards, and achieved many effortless and successful floppy boots into Linux afterwards.
I was very baffled that this only ever effected booting from a floppy and nothing else. I don't recall having to rewrite those floppies that were made before this fix. They just worked afterwards.
I was a young amateur though and maybe it was something else I did that fixed it, but this is how I recall it. It was a pretty frustrating and significant effort though, so I'd think that'd somewhat increase my odds of remembering the important parts. :)