That's a proprietary board with a mostly non standard mounting layout and size.
Even if you don't care about about front IO ,
you're going to have to make sure the board clears all of the case surfaces and doesn't interfere with any of the drive cages if it's that long.
EATX supported cases...
It is indeed.
3GB should be addressable put of the 4 installed
If it works on a G5 , no reason it won't work on a C2D.
SATA is SATA.
TRIM support is questionable on an older OS though.
@LaatSahab
If you've got an old SATA SSD lying around , it'll make a big difference to the responsiveness...
@Popsicleed
If this is your first build and you plan to DIY it,
DO NOT RUSH IT.
The age of the old cabinet is irrelevant as long as it's ATX and not some proprietary Dell / HP / Lenovo prebuilt.
You might miss out on USB 3 and on the ventilation front till you get a new case.
Check the...
If you're okay with 60Hz , it can do the following
Display Resolution 4x 4096x2160 @ 60 Hz
If you need a higher refresh rate , something like an A2000 will work.
Pretty sure @codwapeace is referring to the 4/5 condition mentioned by the OP when he's talking about grading.
Back on topic,
Is the dust optional or a permanent add on ?
Minor item ,
But also add decent quality display cables of appropriate length to your list of things to get.
As well as power cords , extensions etc if required.
Updates usually get pulled if there are issues reported.
Not uncommon for a version update.
Also not uncommon for OnePlus.
Also they release them in batches so all you can do is wait
A factory reset is unlikely to trigger it.
This.
Assuming the 3060Ti was enough for your friends needs , considering the possibility of you'd get x for your card so add y and get a new card is unnecessary.
Card for a card is what I'd push for.