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What to do if my computer is infected by a virus or a malware?

What's the best way to clean a computer with multiple accounts infected with spyware, viruses and malware? Should you install and run software to remove the infections on each account? If you install the software on one account, will it clean the entire computer including each account?

For example, some programs like CCleaner will install only on one account and not offer the option for all users (accounts). Does this mean the program will clean the entire computer including other accounts or do I have to install CCleaner on each account to clean up each user's account?

7 Answers 7


The best way would be to wipe the harddrive and then reinstall everything, reinstalling the anti-virus program first, then anti-spyware. This will fix all the accounts.

The details for whether a malware removal tool will affect all accounts or just one is dependent on that particular tool. However, wiping the harddrive will guaruntee every trace is gone (usually). Malware removal tools may leave pieces of malware scattered about.

  • 1
    +1. you could quite easily spend the same amount of time required for a rebuild on chasing your tail trying to remove nasties as other ones come back in the background.
    – Kez
    Aug 23, 2009 at 21:21
  • +1 totally agree, some infected windows are downright impossible to clean up.
    – deddebme
    Aug 24, 2009 at 1:56

I usually use malware bytes to remove stubborn viruses. Most of the time it is much better to just nuke the hard drive and freshly install the operating system. A deep rooted virus can take vital system files with it whenever you try to remove the virus. This can cause instability and cause a lot of system errors. If you do decide to use a removal approach instead of a reformat, make sure that you use 2 or 3 well known virus removers since not every kind will catch every strand of virus.


You also should boot up the computer in safe mode, because anti-spyware/virus software may not be able remove infected files in normal mode.


I'd suggest:

  1. Running a virus scan from one of the various anti-virus boot disks e.g. the Avira rescue disk.
  2. Then backup all the stuff you want to hang on to.
  3. Reformat the HDD and reinstall the OS.
  4. Reinstall a good anti-virus program.
  5. Set up users with a limited (not administrator) account.

Spy/ad-ware can be a nightmare to get rid of and reinstalling Windows has the benefit of increasing speed of the system.


Running something like spybot search and destroy from an admin account will scan the whole disk. It depends on how bad the infection is if this is worth the effort. After a certain point it's better to just bite the bullet and do a clean install after backing up your data.


Whilst I agree with nuking the hard disk, sometimes it's not always practical. Say for instance you have some rare software you can't reinstall because you don't have the original media or keys and can't afford to replace it. This happened recently to a friend.

On the other hand, some things just can't be cleaned - I've seen instances of Windows where every single .exe and .dll has been terminally infected. However, I'd say quite a bit of malware and spyware can be recovered from. In which case I'd either put the offending hard disk into another PC to clean or boot from a live CD such as created using BartPE.

Another thing with spyware etc., no single product fixes everything so you may have to try several things. You may even have to resort to editing the registry and removing files manually. Google is your friend - somebody somewhere has almost always been in the same position.


Famous quote from Aliens seems appropriate here.

But seriously, without wiping and reinstalling the OS there is no way to be sure. If you absolutely can't reinstall you at minimum must boot from a different drive to clean it.