So I have an old ATX case that I had an issue with the green power LED. When I pulled the LED out of the system, I found a lot of black residue on the internal metal contacts. That's why the LED was putting out little to no light at all and was very hard to see. This case has a red LED for a HDD light and it works fine.

Well, I also have an older ATX case that uses two green LEDs. So here's what I did. I went to a hardware store and picked up a 5V RED LED, some desoldering wick, some solder flux (because I've never had flux before and I occasionally do PCB repairs), and some heat-shrink tubing (never had these before either). I took the HDD green LED from the 2nd case and de-soldered it from the cables and replaced it with the new red LED and did the heat-shrink on the legs. Put it back in the original case and yay!

Then I took that green LED and used it to replace the burned-out one from the first case, also using heat shrink on the legs. Put it in the case and FINALLY got it working.

I'm sure not many people will care, but it's a DIY fix on an old late-90s ATX case... and it wasn't hard at all, so maybe other people might get inspired to do their own fixes instead of just buying new cables or cases or whatever. It's amazing just how many things can actually be FIXED to work again instead of throwing them away and replacing them (like phones or appliances).