I tend to be the extended family / friend computer guy. The new generation of viruses and malware are so hard to get rid of that my policy is this: buy an external drive for your personal documents, because when I get your infected computer it's going to get wiped and reinstalled.
I can count on the fingers of one hand (with a few left over) the malware I've come across that I
couldn't get rid of. Even the rootkits can usually be detected and removed, although it can be a chore.
Much more common are cases where I elect to wipe / reinstall because it's just easier and faster, and the client has nothing especially important on the machine in terms of software. Documents, email and so forth can be backed up. And with more and more people using webmail services that save everything server-side, even the mail is often not a consideration.
For what it's worth, I've found Windows 7 64-bit to be the most robust Windows yet in terms of malware-resistance. On the flip side, however, it's also the most difficult to clean up once it does get infected (well, other than Vista, which is a total nightmare...).
As for FaceBook, MySpace, BeBo, and other social networking platforms, they're a scourge, in my opinion. I am this close ( * holding thumb and forefinger half an inch away from each other * ) to putting a clause in my warranty language that nullifies the warranty if the user so much as
thinks about logging on to those sites. They're even worse than KaZaa and its ilk used to be. Anyone can post a link to anything, and the naive users happily click away and infect their machines.
My warranty specifically excludes malware reinfection, but I tend to honor calls anyway if they happen soon after the service, just on the possibility that I missed something. But these social networking sites are festering pits of digital perdition, especially for inexperienced users, and no AV software I've come across can keep up with the constant barrage of malware linked to from FaceBook
et. al.
I had one machine a few months that was used by a teen-aged kid who wasn't home when I did the service. I went over her computer, found that she had absolutely nothing of importance on it that couldn't be backed up, and decided to do a reformat / reinstall in the interest of saving the client some money. I did a clean install from DVD, installed virus protection (Norton, at her father's insistence and against my advice), did all the OS and other updates, and left the machine pristine.
She got home from school at about 3:00 p.m., immediately logged into FaceBook, and was reinfected by 4:00 p.m. Seriously.
The father called me and demanded that I come back immediately to re-clean the machine, despite his daughter's admitting that she'd turned Norton off to access whatever it was she was trying to click and that Norton had been blocking. This idiot kid got a virus warning, saw that it was viral and being blocked, and disabled the AV to access it because "she wanted to know what they were saying about her." It's like an obsession.
I decided to cut my losses. I mailed the father his check back instead of doing the callback. These kind of clients aren't worth having. His "can-do-no-wrong" kid admitted to deliberately allowing the machine to be reinfected, and I'm supposed to clean it up again for free? No thanks. Call someone else next time, and here's your money back.
-Rich