Free anti virus

There are two possiblities

One your old anti-virus setting is not remove from your PC.
Install **** cleaner (ccleaner) to get rid of the anti-viruses left over setting in the windows registry.
http://www.softpedia.com/progDownload/CC...

Two - a virus is preventing you from installing anti-virus
Use another clean PC to download Clamwin portable anti-virus and install it on a USB pen drive.
http://portableapps.com/apps/utilities/c...

Document on how to configure ClamWin
http://support.real-time.com/open-source...

Start Clamwin anti-virus and update the latest anti-virus definition files.
Select the tools menu bar, set the preferences to remove virus.
Start the infected PC in safe mode by pressing F8 during start up.
Run the Clamwin Anti-virus on the USB pen drive to scan the infected PC.

or

If you have tried all the various AV Removal Tools to look for expired/leftover remnants of other AVs, I'd suggest scanning your System for Malware.

Malware will often stop you downloading Security Products.

Download, install, update and scan with each of the two programs below to check for/remove Malware/spyware.

If necessary, do all the above work in Safe Mode with Networking.

To get into Safe Mode with Networking, tap F8 right at Power On / Startup, and use UP arrow key to get to Safe Mode with Networking from list of options, then hit ENTER.

Read all info below before starting:

http://www.malwarebytes.org/mbam.php

Malwarebytes is as the name says, a Malware Remover!

Download the Free Version from the link above.

Download, install, update and scan once a fortnight.

http://www.spybot.info/en/index.html

Spybot Search & Destroy 1.6.2 is a very good, FREE Anti-Spyware Program.

Download, install and update it.

Then SCAN with it.

Update it, and scan your System once a fortnight.

hope this helps

Even if you running anti-virus software, it may be beneficial to scan your PC with another scanner to check for viruses. No anti-virus software is 100% perfect at catching everything. Here are a few good free online virus scanners that you can run to check your PC:

http://security.symantec.com/sscv6/home.asp?langid=ie&venid=sym&plfid= 23&pkj=RRJEDTKJBTVISBYWWYP

http://onecare.live.com/site/en-us/default.htm

http://www.eset.com/us/online-scanner

http://www.pandasecurity.com/homeusers/solutions/activescan/

An excellent free utility for overall system maintenance is Advanced System Care Free ( http://download.cnet.com/advanced-systemcare-free/3000-2086_4-10407614 .html ). I use this utility on a regular basis.

You should always run anti-virus software. There are several very good, free, anti-virus products available. One good source to read editor and user reviews, and safely download anti-virus software, is http://download.cnet.com -- search for free antivirus software. In addition to the reviews, you can see how many people are downloading the software, which is another good indicator of how popular it is.

I have used AVG Free ( http://download.cnet.com/avg-anti-virus-free/3000-2239_4-10320142.html ) , and Avast Free ( http://download.cnet.com/avast-free-antivirus/3000-2239_4-10019223.htm l ). Both are very good, and completely free. At present I am using Avast on all of my home computers.

I have heard good things about Avira AntiVir Free ( http://download.cnet.com/Avira-AntiVir-Personal-Free-Antivirus/3000-22 39_4-10322935.html ), and it has good ratings, but I have not personally tried it.

In addition to Avast or one of the other free anti-virus software packages, I also run Ad-Aware ( http://download.cnet.com/ad-aware-free-internet/3000-8022_4-10045910.h tml ). Ad-Aware is a free anti-malware, anti-spyware package.

Good luck!