Although it depends on which employee is doing the virus removal and of course the actual virus itself, The Geek Squad has a few unusual tools at their disposal, such as a customized safe mode enviroment that allows them to run scanners with less of the computer loaded and a bootable live CD which allows them to remove stealthing and polymorphic viruses that infect the core windows files itself. Plus some people will do a manual removal from a Windows XP RC session, or a WinPE enviroment. In any removal, a somewhat large portion of the work done is manually. Especially with newer viruses infecting restore partitions.
In other words, contrary to popular belief, in most cases it's not just running a virus scan, which in any case will not remove most of today's larger nasties. Running a simple virus scan on a truly infected computer is like putting on a raincoat after you've been in the rain for an hour - it's not going to do a whole lot for you. It may remove the visible symptoms, but in most cases your computer is still infected.
Three and four years ago a simple virus scan or two would have cleaned up most things, but right now the malware writers have the upper hand. And if you don't believe me, ask around at Kaspersky Labs, Symantec or Trend Micro. Just a few weeks ago a Trend Micro executive was stating how the AntiVirus companies are failing at their job.