The 'K' icon probably belongs to "Kaspersky Antivirus" but it should be red when it's working okay and up to date.
If it's grey it usually means the trial version (or the subscription for updates) has expired.
If you go in to Control Panel > Programs & Features you should find the Kaspersky software listed there if I'm right about the icon. You can uninstall it from there and the icon should no longer be there after restarting Windows.
However, you should really not be running the system without some up-to-date antivirus software, so choose one and install it as soon as possible, certainly before downloading anything else (except antivirus software of course).