Your kinda twisting my words (I didn't mean all free AV are crappy, but compared to already paying for Kaspersky or some of the other quality ones - yeah it is)...
If you want a source, how about softapedia?
http://news.softpedia.com/news/AntiVirus-Free-Vs-Paid-Detection-139005.shtmlWhile free AV can be good and can even out-performance some paid AVs, some decend paid versions are a lot better and stronger for overall protection. Kaspersky Internet Security is designed as an overall protect, not just a anti-virus scanner and/or firewall. It also checks ad-ware, malicous software, registery, application controls, riskware, anti-spam, anti-popup, anti-scripting, instant messager protection, anti-banners, anti-phishing, suspicious sites, network attacks, security analysis, informs you of security risk software requiring updates, even parental control, etc. Compared to already paying for all that vs a freebee, I think it leaves any free AV in the dust.
If you didn't want to paid AVG and Zonealarm, while I personally find them annoying, could still offer some good protection. Maybe they could be better options over memory hog Mcafee or the basic version of Norton, etc.
If you do go for a free version, ensure it's just real! For example: Anti-virus Pro 2009 is a trojan downloader hiding as a anti-virus. Lots of the freebee anti-trojan software are in fact trojans themselve, it's the easy target people searching for protection must be without a defence, upload a trojan for them instead. Just be careful and ensure you get it from a trusted source like download.com.
Anyways, what version of Kaspersky are you using? Are you using 32 or 64 bit OS?
Kaspersky released newer versions of their software as soon as Windows 7 beta was launched, previous version will have issues on Win7, but you should have the latest from their website which will support it.