Bad advice. Once you've been compromised, you can't really be 100% sure your computer has not been compromised in a way that is currently detected by most virus/malware scanners. Not to mention that a virus/malware may have done damage that removal process cannot fully fix. Sure, under Windows you can run sfc /scannow to fix critical Windows files but who's to say that the source database for these files have not been damaged too.
You're right, but it varies depending on the system. I do this sort of thing for a living in business which, to be perfectly honest, thinks a backup is what you do when you fall over. So naturally the servers are full of stuff that has no copy anywhere else and cannot be formatted ever. Yes, it's dumb and stupid but I'm not allowed to fix it. Anyway, that required me to find alternate ways of getting these mission-critical servers clean. Mostly, things like toolbars and spyware will just take a blast from MSE or MalwareBytes and you're good to go. But for more threatening issues, that's where you go a little deeper.
That's why I pointed out Hitman Pro, which no one else in the thread mentioned. It is a completely underrated program. I had to fight off the XPAJ virus, which is a sneaky little bug that doesn't just put a shell around an EXE/DLL like everything else, it pulls it apart and inserts itself into it. Strangely, our AV programs were doing more damage to our system trying (and failing) to remove it than it was. It was totally invisible to MalwareBytes and Combofix but Hitman picked it up and got rid of it. Sure, there were some systems that had the thing embedded too deeply, and they needed to be purged, but using Hitman I could watch the virus replicate. The most secretive virus I've ever fought and I was watching it breed. I felt like a voyeur.
Either way I managed to get it fixed. I installed better monitoring software and in four months since the outbreak I haven't seen a single red flag.
Yes, I'm fully aware of how stupid this no-backup setup at my job is, but as a minimum wage peon I'm not exactly authorized to make improvements. If I had a choice I would quite literally nuke it. I think my workplace has a monopoly on cutting corners and they'd rather pay me to work 28 hours over a weekend to fix their problems.