Prefetch appered in XP.
In w7, both Prefetch - Superfetch
IDK about w8, in w10 was called SuperFetch, then SysMain.

I run w7.1 Ult on a very old desktop.
4 GB DDR-2 ram.
Samsung Pro 840 Pro SSD.
I disabled both Prefetch - Superfetch, for a 8% diff in ram usage.
From 56% to 48%,
The system is also more responsive.

For w7 there is a standalone app,
TweakPrefetch v5.3.1.3
It works very well.

If using w8 or w10, one must use a different method, Google is your friend.
YMMV

Just go into services.msc and disable it. Same as for W7 and before under the different names. Snap is from a W10 machine.