ISA/pci/pcmcia nic with bootrom/boot floppy to boot from the network. With this you can connect to a server which allows to install anything you want or start some diagnostics quickly without having to deal to plug in hhd or equivalent + fdd with all their big cables. All you need here is a free slot and an ethernet cable

Fdd cleaning kit : to clean you old 5"1/4 or 3"1/2 much faster and avoid damaging you vintage disks

Isa/pci POST card : to know a bit more what your mobo is doing when it doesn't display anything (this helped me to save a mobo with a dead BIOS chip)

That's all I can think right now

Here are some things that I find useful:

1. CD/DVD lens cleaners - for cleaning CD and DVD drives, I managed to bring some dysfunctional drives back to life with them.
2. PCMCIA CompactFlash readers - for transferring files between a newer computer and an older laptop.
3. PS/2 to AT keyboard adapters - for using PS/2 keyboards on AT desktops.
4. 7-pin S-Video to Composite/4-pin S-Video adapters - for plugging older video cards and laptops into VCRs, DVD recorders, and older TV sets.
5. SATA to Molex adapters and fan splitters/hubs - for occasions where you have some case fans you want to use but find yourself running out of spare Molex connectors to plug them into.
6. Drive bay adapters (2.5" to 3.5" and 3.5" to 5.25") - Ever want to use a laptop hard/solid-state drive in a desktop? Do you want to put some extra 3.5" floppy/ZIP/whatever drives into a computer with only 5.25" external bays to spare? If so, then you know why this is here.
7. USB hubs - for when you run out of spare USB ports.

Deksor wrote:

ISA/pci/pcmcia nic with bootrom/boot floppy to boot from the network. With this you can connect to a server which allows to install anything you want or start some diagnostics quickly without having to deal to plug in hhd or equivalent + fdd with all their big cables. All you need here is a free slot and an ethernet cable

Fdd cleaning kit : to clean you old 5"1/4 or 3"1/2 much faster and avoid damaging you vintage disks

I second those two.

Logilink or Rockfire USB 2.0 to 15 pin gameport adapter..
There are few brands ..but a very useful bit of kit to allow use of old joysicks and gamepads old laptops etc.
Sadly these dont work with DOS/Win95 ...but for win98 onwards.
A must for gameplay on older laptops.

..and if you dont have usb 2.0 ...they also work daisy chained using a usb 2.0 port ..pcmcia card
rgds
VS

Dupont set like for example this:
https://nl.aliexpress.com/item/1450Pcs- ... lsrc=aw.ds

PS/2 mouse brackets
https://www.startech.com/Cables/Serial-Parall … Bracket~PLATE6F

blind I/O backplates for installing AT boards in ATX cases
https://www.amazon.com/SuperMicro-MCP-260-000 … s/dp/B003TZQK34
(preferably a lot cheaper than these)

I'd add:
- ISA & PCI POST diagnostic card. It's certainly not always going to tell you what's up, but worth it just for telling the difference between 00 "absolutely nothing" and anything beyond that indicating that POST at least started.
- An EEPROM flasher - or failing that a motherboard or other card with ROM socket that can be used to flash with.
- Soldering iron and supply of good low-ESR caps in various capacitances and voltages.
- White spirit & methylated spirits for cleaning off old thermal sticker/paste residue or other mess on/around chips.
- A nice well-balanced, magnetised crosshead screwdriver that fits your hands well.

>POST isa and PCI card, i agree, i always wanted one for my old motherboards but never bought one
>i always wanted a Power supply tester, those are very cheap and got lights. Some of them provide just a light and some got an actual LED screen.
>Dinn to ps/2 keyboard connector converter.
>capacitors, lots of capacitors or kits of them

got another one

a nice set or kit of screwdrivers with magnet. that can save a lot of time.