Hey, JGalt, I used to work for a company that fixed PCs, and this is my take. Kaspersky's a really good product, but there's other stuff out there that's free and will protect you well. You've got options. It depends where you're coming from.
1. If you need to clean up an already-infected Windows PC, the free Kapersky boot disk is really good. You would need to download it on a non-infected PC and either burn it to CD/DVD or do it as a bootable thumb drive. Then you boot to it in the infected PC. What it does is it loads a Linux distro along with Kaspersky and then downloads a bunch of antivirus defs and then disinfects the PC. That way Windows cannot even run while Kaspersky scans and fixes your PC. This is good for fixing a virus-trashed PC, but is not a good long-term solution for protecting an uninfected one.
2. Reinstall Windows from scratch, formatting the hard drive in the process. This will kill off any viruses. You'll need to backup any files that are important to you. You just need to do your homework and make certain you know what you're doing. This is a good solution for cleaning up an infected PC if solution #1 doesn't work. Immediately after doing this, install an antivirus application like Avast or Kaspersky (see below).
3. Use Linux instead of Windows. This is what I do. Formatting the hard drive an installing Linux as your OS will kill off any viruses and make it unnecessary to use any antivirus software in the future. I use Kubuntu Linux on my PCs. I've found Linux-based software for almost every one of my needs. Any malware written for Windows will not run on Linux. It is theoretically possible for a Linux PC to get malware, but it's extremely unlikely. I run a thing called WINE that lets me run some Windows software under Linux, and I use VirtualBox to run Windows under Kubuntu for a couple programs that won't run under WINE. Linux is a great solution for someone like me who's tech savvy or for someone who's not tech savvy, but has a tech savvy friend to set up the PC. My computer novice roommate also uses Kubuntu, which I set up for him. When you run a Linux distro like Kubuntu as your main OS, you say goodbye to malware.
4. Avast Free antivirus is a really good antivirus application. It will protect a Windows PC that's not already infected. Since I rarely use Windows anymore, I don't want to pay for an antivirus program. Avast does the job really well on a little Windows 7 netbook that I don't use that much. It's light on system resources, and you don't have to pay a cent for it.
5. If you want to keep using Kaspersky, don't even think about paying full price for it. All you need is any legitimate license for it, and you can use the latest version. Search on Amazon for an old version of Kaspersky that has not been used. You can probablly get that for half or less than half of Kaspersky's full price. Then when you get it in the mail, download the latest version of Kaspersky and use the license key that you got from the old version. I've gotten Kaspersky Internet Security for around 20-25 bucks instead of 80. Kaspersky is a quality application, but don't overpay for it.
This isn't exhaustive. There are other options. There are other good antivirus applications and other good distros of Linux. The most important thing is to arm yourself with knowledge. The huge computer companies want you to think you have to buy a new PC every two years. You don't have to.
