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Yesterday I installed a new Antivirus as my old licence was not valid anymore. I chose the free Avast. Now the pc is extrem slow. It takes about 8 min to start (before with Kaspersky it took 2 min). Is there something I can do?

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did you remove the old Antivirus (Kaspersky)? – Simon Apr 12 '13 at 6:39
no, i did not. How can I do that? – user215113 Apr 12 '13 at 6:48
Add more RAM? Reduce CPU load? Get an SSD? get a different AV app? it is hard to say what is wrong other than your AV is adversely affecting your computer. All you have told us is "I installed something and now my comp is slow". What does slow mean? Can you provide any quantitative proof of it being slow? Are there specific operations that are slower? What is running on your comp when it is "slow"? Does this behavior persist through reboots? Is it slow immediately after it boots? – MaQleod Apr 12 '13 at 6:51
I think the problem is that I installed Avast before removing Kaspersky. I will try Simons answer and let you know if it helps. – user215113 Apr 12 '13 at 6:55
up vote 3 down vote accepted

To remove Kaspersky products from your computer follow the following steps (by Kaspersky):

  1. download the executable file kavremover.exe.
  2. Reboot the computer in the Safe mode:
  3. Run the file kavremover.exe.
  4. Enter the code from the picture. If you cannot read the code from the picture, click on the button next to the picture to generate a new code.
  5. In the Following products were detected section select the required product to be uninstalled. Click on the Remove button. If you wish to delete some products, it is required to delete them separately.
  6. The removal process may take some minutes.
  7. Wait until a dialog window appears to inform you that the product was successfully removed.
  8. On the open dialog window, click on the OK button.
  9. Reboot your computer.
  10. If you had more than one Kaspersky Lab product on the computer, you should rerun the removal tool and chose that product from the list and remove this too.
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I believe this is only necessary if the existing installation is corrupted. A valid Kaspersky installation is perfectly capable of uninstalling itself from the Control Panel just like any other program. – Havenard Apr 12 '13 at 6:52
Under normal conditions I would agree with you but as he already installed another Antivirus it is safer to do it this way. Antivirus software sits quiet deep in the system and therefore it is hard to say, how the two will interfere with one another. – Simon Apr 12 '13 at 6:58

As it is clearly stated in every anti-virus installer, you must not have more then one anti-virus installed in your computer at the same time or this will happen.

Uninstall your old anti-virus and it should fix the problem.

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I am not sure it is mentioned in every installer, but certainly in several of them. And it is good advice. – Hennes Apr 12 '13 at 8:59

You must confirm performance at startup problem is due to your antivirus and search for logs that will show you what's happening.

You can also try this first :

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