When you install some software the program looks around your computer, then "phones home" with the information.
That's not good, it's doing it unbenownst to you, and telling the company everything that it can find, I.E. passwords, settings, ......
It also eats up your system resources.
if your running Windows 98, you can see what's in your start-up, there's several websites which will help in identifying what's SpyWare and what's not.
Here's a quick how to:
Be careful what you select, don't want to louse up things.