The screwiest one I ran into.. this was MANY years ago... was when I attempted to upgrade a system I had with a IBM 486SLC2 and a VLB video card in it -- I upgraded from (if I recall) 16MB RAM to like 128MB.
First I found out the 486SLC2 was essentially a 386 revamped to fit in a 486 socket, the 386 (and 486SLC/SLC2) only had enough address lines for 16MB RAM! Oof. So I got a real 486 of some kind, only to find that the VLB video card mapped at 80MB. Which was ridiculous, since it was over 16MB presumably it didn't have the 16MB ISA limit, so you'd think the next step up would be 4GB addressing and they could have stuck the VRAM closer to the 4GB mark. But no. This was a long time ago, so the older window managers like fvwm you could boot to GUI with like 8MB RAM usage, and the early KDE and gnome of the era would also run in under 32MB; my main motivation to put in more RAM was actually to run Netscape. Browsers being a RAM hog is a perpetual problem, I actually got the RAM mainly so Netscape would run decently; Netscape 0.9-4.0 didn't use much RAM, but other programs weren't as graphics-heavy as a 1990s-era web page so everything else used less. So eventually either code or cache would start using RAM above 80MB. The screen would corrupt (as code or disk cache overwrote the VRAM), then of course the GUI would draw to the screen and overwrite whatever code/cache was in there, the system would of course crash moments after that.
So then I needed to replace the video card too! I think I may have actually downgraded to an ISA card I already had to get it running, slow but no memory conflicts. Eventually I went with a socket 7 motherboard, AMD K5 then K6 then K6-2 (in the same motherboard, I think socket 7 lasted almost 10 years), and PCI video card. (My recollection is I found a motherboard where it had like both SIMM and DIMM slots, so I could move my old RAM over.. that 128MB RAM was expensive!.. so when I upgraded the RAM later I just popped out the SIMMS and threw like PC133 or whatever in it...) Problem solved.
As a side note, I have no big nostalgia for retrocomputing. The systems of the 1980s (Atari 8-bits and ST, Commodore 64/128/Amiga... I guess the Apple II but not a fan... CP/M systems..), those had unique features and are worth preserving, although it's easy to just run the stuff in an emulator too. The PCs I used back then? I don't have nostalgia for spending over $10,000 a GB for RAM, $1,000 a GB for disk, and $10,000 per ghz of CPU power (well, you couldn't get a 1ghz chip in the 1990s, but I mean my first Linux box had a 386SX-16 (0.016ghz), and I'm sure that cost more than the $160 that would make that come out to $10,000 per ghz.)
My Coffee Lake (that I picked up for $180 used) has over 200,000x the processing power of the Atari I started out on; I'm not even going into the 8088-based DOS box my parents bought when I was roughly in junior high. The 386SX-16 I started out on with Linux (after Atari 8-bit and a DOS PC)? With 4MB RAM and a 40MB -- not 40GB -- HDD? My Coffee Lake has about 20,000x the CPU power, 8192x the RAM, and I have 20TB storage now (which only cost about $300 or so total, HDD costs have dropped through the floor of late), so I actually have like 500,000x the disk space.
To be fair, though, it's only 50,000x the storage compared to very shortly, I didn't wait long to replace that 40MB hard disk with a larger one. (Besides being tiny.. it was not IDE. it was RLL and pulled from an older system since the disk in it died. ST250R, since it was RLL it showed up as "/dev/xda" (x for "XT controller" versus the /dev/sda for SCSI... and every other disk interface in newer Linux kernels.. or /dev/hda for IDE.) Linux bypassed the ROM on the card so it got about 4x the disk speed it did in DOS, that only got it up to about 1MB/sec.. but since the disk was so small that let it read the entire disk in 40 seconds.
