The bottleneck is almost always the drive
If a laptop still has a mechanical hard drive, that is the problem, and nothing else you do will matter much. A spinning disk reads at a fraction of the speed of an SSD and everything waits on it: booting, opening a browser, switching between windows.
Moving the same machine onto an SSD is the single biggest change available to an older laptop. Machines that took two minutes to reach a usable desktop reach it in fifteen seconds, on the same processor, with the same software.
Memory is the second thing
Eight gigabytes is the floor for comfortable browsing now. At four, the machine is constantly moving data between memory and disk, which puts you back to waiting on the drive.
On most laptops more than a few years old this is a cheap, quick upgrade. On recent Apple silicon Macs and many thin Windows machines the memory is soldered to the board and cannot be changed, which is worth knowing before you plan around it.
Cleaning software does not do what it says
Registry cleaners, optimisers and boosters do not address any of this, and some of them make things worse by running constantly in the background. There is nothing to clean that is causing the slowness.
What does help, free, is removing software that starts with the machine and is never used.
Heat is the other cause
A laptop that is slow and hot and loud is throttling. Dust packs the heatsink over a few years and the thermal paste between the processor and the cooler dries out, so the machine deliberately slows itself down to stay within temperature.
A strip, clean and repaste restores it. This is the same job that fixes a games console shutting down mid-session, for the same reason.
When it genuinely is finished
A machine that will not take an SSD, cannot take more memory, and no longer receives security updates is at the end. We will tell you that rather than sell you an upgrade that buys six months.
The honest test is what the upgrade costs against what a replacement costs, and we will do that arithmetic with you at the counter.