Spybot S&D (download, check for updates, read the tutorial and scan often, it also does some blocking)
SpywareBlaster (a blocker only, download it, check for updates, enable it and leave it alone except for checking for updates occasionally)
SpywareGuard (similiar to SpywareBlaster but works in a different way and does not update as often for that reason.
Ad-Aware SE (a scanner, download, check for updates, read the directions and scan.
cwshredder (stand alone unit)(another small scanner for certain things, ALL other windows should be closed)
I need to buy software for spyware and adware, but I do not know which is the best one. Can anybody give their valuable advice.