Spyware comes in many forms.  Usually spyware is sending information about your surfing habits so ads can be geared to your interests.  There is little or no good to come from spyware.  It is best if you do not have it on your computer not only for your loss of privacy, but also loss of valuable resources.  Spyware will cause the computer to slow down, the more spyware installed, the slower the computer will be.

You should update your spyware tools weekly.  If an update does not appear for a few weeks, check the website and/or reinstall the latest version of the application form the website.

Run it at least weekly since new spyware is emerging all the time to assist those in helping themselves to your privacy data.  This sounds a lot like the requirements for antivirus...spyware saps the life out of a computer sometimes worse than a virus.

Check this link:
DO YOU HAVE PARASITES?

Here are two very good and popular spyware detection/removal tools.

Ad-Aware (free version)
Or
Spybot

Coming soon Microsoft Windows Defender formerly Microsoft AntiSpyware