have you looked at task manager / performance to see where the bottleneck is? Whatever is hitting (and staying at) 100% is most likely what's slowing you down.
Do you have all drivers updated in Windows 10? Or are you running "OTB" drivers? (out of the box / included with Windows 10). Firmware up to date on the motherboard?
Did you check Windows startup to see what's loading on startup that might be slowing things down? (task manager - startup tab)
Is there a Windows swapfile / pagefile on the 8tb HDD? Read more about that here: https://www.techtarget.com/searchwindowsserver/definition/swap-file-swap-space-or-pagefile
(swap file / pagefile on a slow spindle HDD will kill system performance if windows starts using it. And Windows can be dumb and use it even when there is system RAM available)
I did check task manager when it was lagging bad but nothing was over 60% during startup.
Ill have to look again shortly, currently running another round of memtest86.
Sofar cpu stress tests, disk info, memtest has all been fine.
When I put the pc together in 2021 i installed fresh win10, updated it, installed bigbox,drivers, etc and never had it connected to the net untill a year or so later when I updated bigbox and shortly after had issues ever since.
Yesterday and today i fully updated win10, installed latest nvidia drivers, made sure mobo drivers up to date, the only extra thing running in startup is bigbox which i have disabled while troubleshooting.
Interesting about the swapfiles. I read the linked article but it just states how to set a size for them but not how to edit,delete them
Edit#####
Memtest was fine, rebooted and took forever to become reponsive. Task manager took forever to open, cpu use was at 100% but nothing in the process list showed it was using cpu.
Just trying to open a folder took 30 seconds and would trigger a "system interrupt" process in task manager at 100% cpu useage
Seems like after 5 min after startup things clear up.
Bigbox takes 3 min or more to launch, the menu and previews are laggy, games take forever to launch, but if i close and reopen bigbox it runs better 🤦🏻♂️
Edit#2#####
Found a backup of the file/folder structure of bigbox on the 8tb hdd i must of copied over right after I redid my cab a few years ago, i ran bigbox and its running great from the hdd.
The way i have the cab setup is windows, launchbox/bigbox is on the ssd along with all the artwork and preview video files and all the roms are on the 8tb hdd.
I dont know that the ssd is the issue because even after i initially run the normal cabs bigbox (not the backup i just found) it runs laggy and like crap but if i exit bigbox and immediately launch it again it runs fine.
I updated bigbox a year or so ago, the backup was an older version, not sure if the issue is a bigbox version bug, a windows bug or what at this point.
Contemplating just deleting my bigbox/launchbox folder off the ssd and copying this older build back over to it.
Right now i have my usb hub, ipac4, and 2 led64's unplugged just to rule out those as an issue.
I think i remember updating the k-lite codec pack at some point as well, that made me remember all the runtimea and direct x9 needed for some of theae emulators and wonder if a windows update broke one of those or something as well.
Uggg, these damn builds get so complex its almost needed to just start over 😔