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As you are already infected we must do a lot more than would be needed just to keep your computer clean.

You must have a firewall. I assume you are using the Widows Firewall and it is enabled.

You must have full time (active) virus protection and full time spyware protection.

All the following programs are free.
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Update your antivirus and run a full scan in safe mode

If you do not have full time (active) virus protection install (only one) all are excellent:

AVG Antivirus 7.5 Free Edition
or
Free antivirus - avast! 4 Home Edition
or
AOL Active Virus Shield
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Install Windows Defender (full time spyware protection)
Automatically updates and performs a full scan weekly.
This time only, update and run a full scan in safe mode.
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Install the following five programs and run weekly or at least monthly. You need all five. They will greatly increase your protection. They are not a substitute for full time spyware and virus protection.

Ad-Aware SE Personal (update + full scan)

Spybot Search & Destroy (update + immunize + scan)
Do not enable Tea Timer and SDHelper
After installation: update + scan + immunize

SpywareBlaster: Update then open and click “enable all protection”.

SUPERAntiSpyware free version: (update + scan)

CCleaner: Do not install toolbar option
Removes tracking cookies, unneeded files, history
In options.
Set to run when computer starts.
Place cookies you want to keep in save list
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Note if a scan detects a problem but is unable to remove, start the computer in safe mode with the internet line disconnected and run a full scan.

In severe cases your system restore files will also be infected. In these cases you will need to turn off system restore to prevent malware hiding in the system restore files and reinfecting the computer during removal or during a future system restore. Turning off system restore deletes the system restore files.

Right click on “my computer”> Properties > System Restore Tab > Check box turn off system restore

After the malware is removed turn on system restore.
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Run this time only.
These are specialized removal tools.

CWShredder: run

Roguefix.bat

Shoot The Messenger

SmitFraudFix

Vundo Fix and
VirtumundoBegone (if VundoFix does not work)

VX2 tool for Ad-Aware and run tool (Install and run)

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Additional run this time and monthly.

Microsoft Update “Custom Mode” install everything

Microsoft OneCare Live, run “full service scan”
Updates windows, virus and spyware scan, disk cleanup, disk fragmentation (if needed), backs up registry and then cleans registry, and checks for open firewall ports

Malicious Software Removal Tool (run “full scan”)
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RootkitRevealer v1.71

Rootkit Removal Guide

Rootkits Removers
Pick any 2 install and run one each month

AVG Anti-Rootkit

F-Secure BlackLight

Sophos Anti-Rootkit
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Online Free Scanners:
Run Trend Micro, Kaspersky, and Panda Scan this time.
Run a different one each month.

Trend Micro: HouseCall Free Scan (removes what it finds)
BitDefender Online Scanner
Kaspersky Labs Online Scanner
McAfee
Panda ActiveScan Free Online Scanner ?
Symantic Online Scanner
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Additional Information read: -

Either of them are good, and easily available from your local electronic stores. These are the best in the industry interms of catching viruses and spywares. Also important is getting constantly updated with the latest codes to fight those nasty viruses which are popping up from everywhere!

talking of my experience, i find AVG the best.

for Antispyware get Ewido

Download Grisoft AVG 7.5 Anti-Virus,Anti-Malware.(free)

AVG is a collection of anti-virus protection tools that gives you full protection against viruses, worms, Trojans and malware. AVG provides you with all that you need to be completely protected: including a tool for scanning your hard drive and e-mail, as well as a real-time shield to prevent infections.
Top Features

» Provides automatic update functionality
» Its a reliable anti-virus scanning engine
» Provides free Virus Updates for life
» Options to define file name extensions
» Real time protection with resident shield, email scanning …

Spybot - Search & Destroy detects and removes spyware, a relatively new kind of threat not yet covered by common anti-virus applications. Spyware silently tracks your surfing behaviour to create a marketing profile for you that is transmitted without your knowledge to the compilers and sold to advertising companies. If you see new toolbars in your Internet Explorer that you haven’t intentionally installed, if your browser crashes inexplicably, or if your home page has been “hijacked” (or changed without your knowledge), your computer is most probably infected with spyware. Even if you don’t see the symptoms, your computer may be infected, because more and more spyware is emerging. Spybot-S&D is free.

SUPERAntiSpyware is the most thorough scanner on the market. Our Multi-Dimensional Scanning and Process Interrogation Technology will detect spyware that other products miss! SUPERAntiSpyware will remove ALL the Spyware, NOT just the easy ones!
Easily remove over 100,000 pests such as SmitFraud, Vundo, WinFixer, SpyAxe, SpyFalcon, WinAntiVirus, AntiVermins and thousands more!

Yahoo toolbar offers FREE anti-spyware:
Scan your computer for potentially destructive programs.
Review suspicious-looking programs.
Remove the programs you don’t want. Keep the ones you do.

Here is another free anti-virus-
PC Tools AntiVirus Free Edition feature highlights
Protects your PC as you are working, surfing and playing
Detects, quarantines, disinfects and destroys Viruses, Trojans and Worms
OnGuard™ protects your computer against threats in real-time

Automatically checks for frequent updates against the latest threats.

*Never install more than one anti-virus on your PC, as they may conflict with each other. On the other hand, its always good to install more than one anti-spyware.