Here is an easy way to have Kaspersky 2010 for free.
Disable Kaspersky and go to Start -> Run and write regedt32.
Now go to this path:
If you have Windows Vista 64bit or Windows 7, go to this path instead:
Change the key "Beta" to "Release" (right click and select "Edit String").
Now in the same place, search for the "PCID". Right click on it and choose "Edit String".
Now you have to change the 3 last digits to anything else, letters and/or numbers. For example, in the below image, it could be a23 or 12f or 1u3 etc.
Now close the editor and restart your PC. When Windows is loaded, enable Kaspersky and right click on tray icon. Choose "Activate" and then "Activate trial license".
You got 1 month as trial. Every time the trial period is over, repeat the process above. If you don't want to do that every month, you can uninstall Kaspersky and try a free and better antivirus, the Avira Antivir.