Check the system date on your computer. If the system date is wrong, correct it and try to activate the Kaspersky application once again. 

1. Make sure that the digital signature of the Kaspersky application installer is genuine.
2. If the digital signature is invalid or damaged, download the application installer.
3. Try installing the Kaspersky application once again.

Make sure that the latest Windows updates are installed on your device. See the instructions for all versions on the Microsoft website.

In this case:

1. Install Service Pack 1 (KB976932).
   If this update is already installed, proceed to step 2.
   1. Open Microsoft Update Catalog.
   2. Select your operating system version and click Download.
   3. Download and install the update.
2. Install the KB4490628 update.
   1. Open Microsoft Update Catalog.
   2. Select your operating system version and click Download.
   3. Download and install the update.
3. Install the KB4474419 update.
   1. Open Microsoft Update Catalog.
   2. Select your operating system version and click Download.
   3. Download and install the update.
4. Restart your PC and reinstall the application.

For successful verification of the installation file signature in Windows 7 and Windows 8, install the root certificates DigiCert Assured ID Root CA and GlobalSign Root R3:

1. Open DigiCert Root Certificates — Download & Test | DigiCert.com.
2. Find the DigiCert Assured ID Root CA certificate in the table and click Download DER/CRT.
3. Open the downloaded file and click Install certificate.

4. Сlick Next.

5. Select Place all certificates in the following store and click Browse.

6. Select Trusted root certification authorities and click OK.

7. Click Next→ Finish.

8. Open GlobalSign Root Certificates :: GlobalSign Root Certificates :: GlobalSign Support.
9. Find the GlobalSign Root R3 certificate and click Download Certificate (Binary/DER Encoded).
10. Repeat steps 3–7 to install the GlobalSign Root R3 certificate.
11. Try installing a Kaspersky application once again.

Use Kaspersky Virus Removal Tool.

For Windows XP and Vista, use the previous version of Kaspersky Virus Removal Tool.

Administrator privileges are required for viewing certificates in the repository of the local computer.

1. Press +R on the keyboard.
2. In the Run command box (Launch program in Windows XP), type mmc.
3. Click ОК.
4. From the File menu, choose Add/Remove Snap-in.
5. In the Add/Remove Snap-in dialog box, select Certificates and click Add.
6. In the Certificates snap-in window, select Computer account and click Next.
7. In the Select Computer dialog box, click Finish.
8. Click ОК.
9. In the Console Root window, expand the directory Certificates (local computer) and select Untrusted Certificates.
10. If you see any protection software certificates in this folder or one of its subfolders, delete the certificates and then retry installing the Kaspersky application.

If the issue persists, contact Kaspersky Customer Service.