Spyware can be rather more tricky than viruses to remove. With viruses, you'll generally always want to clean every vestige of the infection from the PC. With spyware, that's not always the case.

This is especially pertinent where removing the spyware means that you don't get to use the associated application anymore. Do I care if I have an adware application if it means I get to continue to use the software I want? Some applications have very good checks on them, and sometimes people are prepared to live with the spyware if it means they can still use the software. Ultimately, this is up to the user.

For this reason a good logging and reporting system in anti-spyware is vital. A log system will keep track of deleted files - if you have later problems (such as a needed file being deleted), you can go back and track down what happened.

Detailed information about the consequences of your actions is vital in anti-spyware. Some anti-spyware, for instance, provides a list of hundreds, even thousands, of potential spyware offending elements (files, keys, processes and the like) and asks which ones you want to delete. This is not very helpful. The temptation, of course, is to say just remove them all - which could lead to trouble, since one of the offending elements could be a directory with important documents. Additionally, in some cases spyware will overwrite core system files with modified versions, and the out-and-out deletion of the spyware would often have major consequences for the continued operation of the system.

Look for anti-spyware that provides information about the detected spyware - its effects, associations and dangers. The major anti-spyware software solutions have become much better at this, often warning about associated software that might cease to function if you choose to remove the spyware. A detailed list of spyware effects is also very useful when determining the risk if you choose to leave the spyware installed.