"Fireball" Virus?

I have helped a lot of people with computer problems. They had McAfee and were complaining because their computer was being very slow. I used a 3rd party program to scan for malware present on the machine. I just helped someone two weeks ago who had McAfee. I ran this 3rd party program on their system and McAfee let over 12 pieces of malware and other viruses on the machine. She was so disgusted that she got rid of it and I set her up with Kaspersky and she is happy as ever and her computer isn't slow anymore. Removing viruses can be hard, and a PAIN!!! After my experience with McAfee, I don't trust it. It was the 2009 version that I was using through my internet provider. It promised to have millisecond detection and all that - but if it did, it wasn't working for me. I don't even trust the new version of McAfee 2010 that is out now...
In light of that, I started to wonder, can Windows 7 get viruses? On all the virus reports I see from Symantec (because I have a 3 Macs with Norton on them), all the viruses that I see on the ThreatCon are usually for Windows ME, XP, Vista, etc. None are for Windows 7. But if 2 Trojans were found formerly from my McAfee, then it must that they can...who knows...

That was one unbelievable mess that McAfee had with their signature accidentally getting out of their QA environment. Maybe they will look to change their products to make them better.