using Spybot versus formatting and reinstalling everything

I've read that the only way to be 100% certain a system is clean of spyware is to format the drive and reinstall everything from the recovery partition.

Sometimes I wonder if this is the best option for dealing with spyware? the other day I was removing spyware from someones PC and it took 6-7 hours to fully clean this system. After it was done, I was thinking that I could have formatted the drive and reinstalled everything in much less time.

how do you make that decision? using spybot or just zapping the drive and starting from scratch? spybot now searches for nearly 835,000 variants of spyware... on older slower PCs, it takes a long time to run and do its thing. time is money as they say, so I can't help to wonder if a format and reinstall from the backup partition is a better time saving option than using spybot or any spyware removal program?

what do places like staples, best buy, or office depot do? do they run spyware programs, or format and reinstall?

thoughts?

Well, i dont think there is a need to fromat the system and install it from the scratch, as long as you are not sure, you have a Rootkit or a Virus (backdoor) on your computer, which cannot get secure removed from AV.

The most of Spyware is, if some basicly Security-Settings are set, comming on the Computer with some other Software, which the user wants and decides to install, because the most Spyware is bundlet into Freeware and illegal stuff.
So, in my point of view, this means, as long as a user install this kind of software, willful, because he wants to use it, or he installs this kind of software, because he dont think about what he is installing, it will be only a cycle of installing Software with Spyware, formatting the device (with probably a loose of data), and formatting again.

Therefore i think Spybot is doing a great job and should be, in the most cases, be prefered towards the procedure, you described, at least as long as you knew (from using Spybot) you have something, which cannot get removed.