Is it possible to turn an external hard drive (removable) into a "permanent" one?

Question

Hard disks

I'm trying to make the system less noisy, there is an old 250GB hard drive and an SSD. There is also an external Seagate terabyte "not collapsible" and you don't want to break it. My HDD is purely for data storage and some weak games that an old 4th stump will pull. When testing the speed through Crystal Disk Mark, it showed that the external one is slower than the built-in one in some places, because of this there are some concerns.
I don’t want to buy a hard one, because in 2-3 months I will put 2 more SSDs, m2 and for storage from the new generation of Samsungs.
The speed of the old and external

Can I get rid of the hard drive and connect only my external one?

Answer 1

For a 4th Pentium, I think the speed looks good. A modern internal drive (roughly speaking, from 1-2 TB with SATA III support) will give more speed even with an older SATA on the motherboard, but you yourself say that there is no desire to buy more.
Regarding "transformation": what exactly do you mean? All external drives are "collapsible" (at least, we were able to disassemble them for data recovery), but the probability of damaging the external case "to the point of ugliness" is quite high.
The most important thing here is not this. For most modern external drives, the USB connector is soldered on the board, respectively, there is no SATA there and you won’t be able to connect it just like that.
You can either solder the SATA connector yourself or adapt the board from the same internal drive, but this is not the most trivial task if you have not done this before.

Answer 2

Well, just put Windu on it and see if everything is ok