I'm Quoting some lines from kaspersky Support website
A new option has been added to Kaspersky Anti-Virus 2011 / Kaspersky Internet Security 2011 which allows skipping scan for incompatible software during the product installation.

This option is recommended ONLY if you are absolutely sure that the third-party software was deleted but is still detected by the Setup Wizard of Kaspersky Lab 2011 products. Otherwise after the program installation the operating system may malfunction and even crash.