Many PCs today are full of spyware — programs that lodge themselves inside your PC, spy on your Web surfing, and usually cause problems in the process.

Some just slow down your PC; others place targeted ads, pornography and pop-ups on your PC — sometimes ads appear even when you’re not even online.

Fortunately, three free programs make spyware fairly easy to clean off your PC.  Here’s how to remove spyware from your PC:

First, download and run the free version of this program:

Ad-aware

The first time you run Ad-aware, it will ask to ask permission to download “definitions.” Tell it to connect to the Internet and install them. Once it’s through downloading and installing the latest definitions, it’s ready to scour your PC for the latest breeds of spyware. Click the Start button, and Ad-Aware scans your PC, booting off any spyware it finds.

Next, download and run this program’s free version:

Spybot S&D

Let this program update itself as well, and then tell it to scan your PC and remove any spyware. Finally, run Microsoft’s free anti-spyware program:

Windows Defender (bundled with Windows Vista and Windows 7)

Once you’ve run all three programs, restart your PC. Hopefully, that treatment will have killed the spyware.