Quickest -

1. Take the lid off the source PC put the HDD in it
2. Copy the stuff.
3. Pull it out
4. Put it the other PC,
5. Your done

Formatting the HDD my be optional.

Connect both computers over ethernet and rsync the data across. It will still take several hours over gigabit ethernet though.

Parallel port would be faster than serial, but if you’re using serial I’d go with Z modem for the compression and error correction.

1. Take the drive from PC 1 and attach to PC 2 => copy / paste

2. External drive

rsync over a wired network. That way, I can stop and resume at any time.

If you want the bare minimum fast transfer and both PC are in local network, use Dukto-R6. It’s super basic file copying, you just need to drag and drop.

For more advanced options,the others have already pointed it out.

External usb hdd

You could go over a wired network.

I just transferred 12tb from one hdd to another via usb 3.0. Went at roughly ~180mbps and took 1.5 days

I’ve been sending 10TB from one PC to another on my network over the last 2 days, it’s nearly done. It’s a wired network, and while sometimes I use tools like robocopy for more granular control over the the copy settings and logging of any copy errors, I generally find the standard windows copy tool to be faster.

USB 3.1 Gen2 is hard to beat. 10Gbps. But for HDDs the HDDs themselves will be the bottleneck. For sustained file transfers, perhaps no more than up to 3Gbps, even if installed in the same PC. Good SATA SSDs may manage closer to 6Gbps. NVMe SSDs are likely to saturate USB 3.1 Gen2. Then PCI-e directly between installed drives is the fastest. Normal cabled network is only 1Gbps.

File transfers to/from external multibay USB DAS can be done in parallel, involving multiple HDDs, and come close to saturating 10Gbps USB3.1 Gen2 speeds.

Then there is thunderbolt.

Start a rsync transfer when you go to bed. In the morning it will most likely be done.

robocopy or rsync if you can’t place the drive in the target or an external enclosure.

rsync over sshfs over Ethernet.
I transferred 10 Tb over night, but it depends on how many files do you have.

I would write it to an nvme drive and swap that drive to the new pc

Fastest “normal” way would be write it to a USB 3 drive on machine 1, read from drive later on machine 2. An SSD would be best. Even with having to do the write and read in two phases, I’d still expect it to be faster than a 1G network.

(Less normal ways would be things like Thundrerbolt SSDs, 10G or 40G ethernet for direct transfer, etc. But if you have that kind of tech already in place, then you’re not asking. ;)