PC Pitstop has long been a source of information about unwanted software and how it spreads. Now we're using our test results database to give you weekly updates about which programs are the most prolific. The prevalence numbers indicate the percent of PCs tested at PC Pitstop where we detected that file running. Our detection works by file name, so some products may be listed multiple times if they consist of two or more files. To check for spyware, adware, unneeded programs, and many other common PC problems, try PC Pitstop Exterminate or our full system scan.