There are several reasons I stick to that position.
As a result, every so often I get push-back – often angry push-back – that Windows Defender remains my primary recommendation.
Many Spyware programs are intended to track your Internet browsing habits, such as frequented sites and favorite downloads, then, provide advertising companies with marketing data.
On the other hand, I fully recognize that Windows Defender might not be the right solution for everyone. This is where I run into some difficulty trying to make recommendations. Tools that were once clearly free, have on more than one occasion, moved to promoting their paid product so heavily that the free version virtually disappears.
Spyware often comes in the guise of a slightly useful utility, that does offer some sort of function, such as an Internet Web Search Utility - but at the same time sends your personal information back, such as your hardware you use, which programs you run, what websites you commonly hit, etc. - It was always suspected but now a source reported that practically ALL porn sites (98%) use some kind of spyware to track visitors.
I do have to qualify this with the fact the source is a vendor of spyware tools, so you need to take that into account.
Watch out for poor system resources, running out of memory, lots of hard disk activity or a screen that flickers.
I would share my solution only if I knew it worked)... I researched the top anti-spyware programs and came up with a top three list: (Incidentally, these three, and only these three, are listed on Microsoft's Windows XP's Antispyware Software page, as of the time of this writing. These are strong indications that these software products are worthwhile.) I use three anti-spyware programs, instead of one, as I found each one detected items on my system that the others did not.