Well, nothing's preventing you from it, but you can expect a *drastic* slowdown in responsiveness, a higher RAM usage, and lots of disk activity. Personally, I wouldn't do it. If anything, since you have a license to Kaspersky, use it as your primary AV; then, if you want to have another one, keep the second AV's real-time scanner off (as RSkeens mentioned) and use it to manually scan files. I agree with grandad though, if you've already got Kaspersky, you're already quite well off, it's IMHO one of the best paid Windows AVs out there.
As several other people have stated, it is STRONGLY recommended that you stick to one AV program running at any given point. I have been using Vipre lately, and while relatively new to the market, it seems to be quite good while remaining lightweight.
I've seen so many mixed reviews on Kaspersky that I have been hesitant to give it a try. There's the Kaspersky is a scam camp yelling about how their machines have picked up terrible viruses while running Kaspersky and then there's the Kaspersky is wonderful camp that have never had a problem with anything while running it. Difficult to get the "full story" on any of the reviews of course.
Aside from it being a bad idea, the AV companies are becoming smarter . For instance, I had Avast AV installed, and wanted to install AVG. AVG installer told me Avast would be uninstalled first, I clicked next, and AVG uninstalled Avast, then installed itself .