There is no such fixit tool, because there are an unlimited number of
reasons for a computer running slowly.

Something to keep in mind: Your computer is running much more software
than it was when you first hit the Power button. Windows Updates have
added mightly to your copy of Windows. Your security software is much
more complicated than it was 4 years ago, since it has to battle so many
new types of threats. You have probably added software, and updated your
existing software. The point is: You can't expect a 4-year computer -
even a well-maintained 4-year old computer - to be as quick down the
road as when it was brand new.

Of course, there is all manner of snake-oil and hype on the internet
promising to speedup your computer. You are wise to stay away from that
garbage.

That said, the most prevalent reasons for slow performance -- even in a
1-year old computer - a

* Malware infection
* Too much software running in the background
* Unwise configuration choices.

There is work you can do to possibly zero-in on what may be slowing your
computer...but it will take concerted troubleshooting by you. There
ain't no magic bullet here.
---
Leonard Grey
Errare humanum est

PT wrote:
My Windows XP Home computer is four years old. It works, but has
become increasingly sluggish.

A quick Google on “slow computer performance” yields a modest 35
million hits, Most are for alleged registry fixes, and I suspect that
at least 34.99 million are virus/Trojan plantings or otherwise
worthless.

So what I'm wondering, after all these years, is there an acknowledged
effective tool for cleanup?

If so, what is it?

And by whom/where has it been tested and its effectiveness verified?