Several sites offer various reviews, user’s opinions and rating. Users have different approach to different applications. (Some of them are blind fan also). I have made this review on my own experiment and experience. Obviously a few editor’s remarks from CNet has taken to review some products. I have compiled this document from throughout the WEB (I have no exact word to describe some features

). Hope someone will get helped.
A few utilities (free or Open source) required or necessary for Windows appended below.
After initial installation everyone need Antivirus and Anti malware or anti spyware. Following are useful FIVE (FREE). Most of them are known to all of you. But I have listed them in performance wise:-
I. ANTI VIRUS
(A) Anvir Avira – (23.96 MB)
Free antivirus - Avira AntiVir
Pros - With new Virus engine scanning is much faster. Integrated scanning for malware and rootkits. The heuristic scan can be turned on or off completely or partially, with three different intensity levels. Faster definition update.
Cons - Whenever found a threat it pauses in the middle. It is good for removing the culprits, but you have to remain in front of the PC till scan completes. A nagging screen/ad pops up while updating.
(B) Avast Home edition – (26.19 MB)
Download FREE antivirus software - avast! Home Edition
(One of the all-time favorite.)
Pros - Avast Home Edition guards your PC and the network with multiple shields that scan executable and files. You can select parameters for scanning, and even choose wild cards to exclude specific file types. You can adjust the sensitivity level for the program's detectors when it comes to scanning downloaded files, instant messages, e-mails, and a host of P2Ps. Its efficient interface opens up window after window to tweak its settings to your liking, for novice to advanced level protection. (Cnet review).
Cons – The UI is not impressive. Scanning takes too long, but effective. No proactive protection.
(C) AVG free – (51.2 MB)
AVG Free - Download antivirus and antispyware software for Windows XP and Vista
Pros – Uses low system resources, Anti malware supported. Good in detection, not best.
Cons - Some reported false positives. It erases some user installed programs without prompting.
(D) Rising Antivirus free edition – (54.15 MB)
Pros – Faster scanning, smaller memory foot print. File shredder included.
Cons – Product from China (Several PC owners are worried to use software from China). Basically it is free but still its trial period expires!!!. You can manually update the database. No warning message of the expiry period!!
Important - This company has cooperation projects with Xunlei, a Chinese software program for peer to peer download. Advertisements on Xunlei urges users to download Rising Antivirus and other related programs of the same company. By installing Xunlei and Rising softwares together, price discounts and a prolonged free trial period is given for Rising softwares. Its partner, Xunlei is a controversial program for copyright infringement. Also, Rising Antivirus does not detect certain virus and trojan horses associated with Xunlei. One example is the ignorance of virus which comes with websites that
ѸÀׯìϹ·¹·Ó°ÊÓËÑË÷-Ê×Ò³ redirects. Note that
ѸÀׯìϹ·¹·Ó°ÊÓËÑË÷-Ê×Ò³ is under the Xunlei company. Suspected trojans bundled with the Xunlei software are also ignored by Rising Antivirus.
(E) Clam Av – (23.43 MB)
Free Antivirus for Windows - Open source GPL virus scanner
A lot of people surprised to see this entry here. It is open source and not far behind the paid version.
Descriptions – (Cnet) ClamWin Free Antivirus comes with an easy installer and open source code. High detection rates for viruses and spyware. Scanning Scheduler.
Automatic downloads of regularly updated Virus Database. Standalone virus scanner and right-click menu integration to Microsoft Windows Explorer. Addin to Microsoft Outlook to remove virus-infected attachments automatically.
( I am using it in Ubuntu.)
Some other free choices are COMODO internet security, PC Tools AV,EAV, BitDefender free (Use as secondary scanner, no real time protection available.)
II. ANTI MALWARE AND ANTISPYWARE
(A) Malware bytes free edition – (2.42 MB)
Malwarebytes.org
Pros – Speedy scan, High detection rate, File assassin tool for locked files, Simple UI.
Cons – Free version does not support real time protection.
(B) A Squared free –(27.19 MB)
a-squared Free - Free of charge Anti-Virus, Anti-Trojan, Anti-Spyware, Anti-Dialer and Anti-Worm Software - Freeware!
(A squared anti malware is paid version.)
Pros – Powerful and deep scan, large definition and signature database. Detects things other scanners don't.
Cons – No resident protection for free version, large file size, though it scans deeply, uses a lot of sources. Free version cut down too much.
(C) Spyware Terminator – (632 KB)
Free spyware removal and spyware protection - Spyware Terminator
Pros - Good spyware scanning, 100% real-time protection, HIPS protection, Antivirus protection (Clam AV). Choice for Web security Guard installation.
Cons – Uses more system resources, missing Proactive Defense and Rootkit Detection.
(D) Spybot S &D – (14. 38 MB)
The home of Spybot-S&D!
Pros – One of the oldest in business. Immunize the whole blocks with Admin privilege to prevent unknown attacks. Easy to use TeaTimer and new lower memory usage. Secure shredder is a good addition.
Cons - No automatic updating. Searches for updates when start scanning, Occasional errors.
(E) Spyware Doctor SE – (12.7 MB)
Spyware Doctor Starter Edition - Free software downloads and reviews - CNET Download.com
Pros - it detects viruses, cookies, infections, malware.
Cons – You have to manually remove the detected items .
Following are also considering good applications.
AdAware2008 (22.7 MB) -
Ad-Aware 2008 - Free software downloads and reviews - CNET Download.com
Pro – The adware and malware detection engine has undergone a significant overhaul, resulting in faster scan times and improved rootkit detection. The updater is no longer permanently on, and it instead runs in your system's background only if you activate it.
Con - The antivirus integration, the real-time Ad-Watch guard, heuristics scanning, the scheduler, and plug-ins are disabled in the free version. I have not understood the working style.
Threat fire -
ThreatFire AntiVirus - Behavioral Virus and Spyware Protection
Pro – This is an inbuilt antivirus + anti spyware solution, go fine with other AV
Good detection rate.
Cons – Real time protection uses more CPU while not scanning.
III. The registry is considered the heart of an OS/System. Removing unnecessary registry entries and optimizing it improves the system performance.
Registry Guards, Registry cleaners are important applications for Windows.
CCleaner -
CCleaner - Home
Pros - Crap Cleaner removes unused and temporary files from your system quickly.
Internet Explorer Cache, History, Cookies, Index.dat, recent documents, run, other explorer MRUs, Thumbnail cache, Recycle Bin, Temporary files and Log files etc
Advanced Registry scanner and cleaner to remove unused and old entries. Missing shared DLLs, unused file extn, ActiveX and class issues, type libs, Apps, Fonts MUI Cache, Installer etc..
Backup for registry clean. Uninstaller tool to remove installed application safely, start up customization. Options to keep required cookies etc
Cons - Not fix the broken links, A little bit details about the diagnosis will be useful. A few users complained
Wise registry cleaner -
Free Registry Cleaner | Disk Cleaner
Pro – Cleans registry to improve performance. Detects registry errors that other program misses.
Cons - optimization included in paid version. Do only registry cleaning.
I have more to add, but time not permits. I will update the review with defragment tools, more registry fixing tools, Multimedia, word processors etc with their paid companions.