Empty the Prefetch folder, disable Superfetch, keep RAM free — these three tips have been copied for twenty years. All three misunderstand what the caches are for. Here are the facts.
"Delete Prefetch, Windows will fly." It will not — it will do the opposite, measurably. This page takes the three most repeated cache myths in the technician world and checks each against what Windows is actually doing: the Prefetch traces, the SysMain service, and the standby memory that RAM-cleaner apps love to destroy.
Every time you launch a program, Windows records which files it needed in a small trace file inside C:\Windows\Prefetch. Next launch, Windows reads the trace and loads those files in the right order before you ask — that is why the second launch of an app is faster than the first.
The whole folder is normally under 50 MB. Windows caps the number of traces and prunes old ones itself. There is no version of events where emptying a 50 MB accelerator folder makes a PC faster — and the measured effect of deleting it is the opposite: every app pays a slow "first launch" again until its trace rebuilds.
This tip survives from a misunderstanding of the Windows XP era and refuses to die. The facts:
The only honest reason anyone touches Prefetch is forensic privacy on a shared machine — a trace file does reveal which programs were run. That is a privacy trade, not a speed tip, and it costs launch speed every time.
SysMain watches which apps you use at which times and preloads them into free RAM before you click. Two honest cases:
Disabling SysMain is a diagnostic step a technician might try for an hour, not a lifestyle. If disk usage stays at 100 percent with it off, SysMain was never your fault.
Task Manager showing most of your RAM "in use" alarms people into downloading RAM cleaners. Look closer: the biggest slice is usually standby memory — cached files Windows keeps in RAM because RAM is thousands of times faster than even an SSD. The moment an app needs that memory, Windows hands it over instantly. Standby memory is a cache doing exactly its job.
"RAM booster" apps work by forcing Windows to dump these caches and trim every program's working set. The result on screen: a satisfying free-RAM number. The result in reality: everything you switch back to must be re-read from disk and re-paged, so the PC gets slower — you paid real performance for a prettier graph.
When a PC is genuinely slow, the evidence-based list is short and boring:
Notice what is not on the list: Prefetch, SysMain and standby RAM. Leave the accelerators alone and fix the actual bottleneck.
See every cleanup location opened live on a real PC, in the same safe order, step by step.
▶️ Watch Full VideoNothing is broken — Windows rebuilds the traces as you launch programs. You will notice slower first launches for a few days, then normal behaviour returns. Nothing needs restoring; just do not make a habit of it.
There is rarely a reason to. On an SSD its benefit shrinks but so does its cost, since it only uses otherwise-idle RAM. Disable it temporarily only as a diagnostic step if you are chasing 100 percent disk usage — and treat a mechanical drive, not the service, as the likely root cause.
The number is real and the benefit is fake. The app dumped caches and working sets, so the graph looks empty — and every program you return to must reload from disk. Windows manages memory well on its own; standby cache is a feature, not a leak.