Adware/Spyware removal tools
Spy Sweeper [download free trial, ranked better than Ad-Aware and SpyBot in study done fall 2004 -- alice ttlg]
CWShredder [download free trial -- alice ttlg]
Ad-Aware SE Personal - Lavasoft
Spybot Search & Destroy
[use the above programs to check for and remove spyware and adware programs, then if there's still problems, try the ones below -- alice ttlg
HijackThis, CWShredder, & StartUplist [download HijackThis here, plus tutorial and link to support forums to help decide what to delete -- alice ttlg]
Computer Cops - HijackThis Log Tutorial [good details on the logs -- alice ttlg]
Spychecker: HijackThis [another site to download it -- alice ttlg]
avast! antivirus software - computer virus, worm and Trojan protection by ALWIL Software, free version for home use, inexpensive versions for commercial use and for Windows SBS 2003.
Eric Howes' Privacy & Security Page [links to bunches of anti-virus, anti-adware and anti-spyware programs, he also conducted a study last fall on adware/spyware which is discussed in WindowsSecrets' article, Anti-adware misses most malware -- alice ttlg]
Housecall free online virus Scan from Trend Micro
Kaspersky Labs - antivirus protection - protect your cyberspace
Lavasoft Ad-Aware US site
Lavasoft Ad-Aware German site (in English)
PocketKnife Peek, an Outlook add-in for screening your e-mail as plain text before opening it in Outlook. The add-in can be used to view all Outlook message formats, but is aimed particularly at averting the threats lurking in HTML mail. A convenient tabbed view lets you easily examine the message in plain text, HTML source (if any), Internet header, and attachments.
Spybot - Search & Destroy (main site)
Spybot - Search & Destroy (second site)
Trojan Defence Suite anti-trojan system for Windows