REDMOND, Wash. -- At a crime scene, evidence can turn up in a fingerprint, a footprint, in DNA left behind.

But some key clues can be harder to spot. They're hidden inside a computer.

They could be emails - a robber bragging about a crime spree - or evidence of a cyber crime, like trading child pornography.

Hundreds of cops and prosecutors from around the world are at Microsoft this week learning to use technology to track down criminals.

They say nearly every crime has a computer connection, but not every department has the personnel or expertise to crack it.

Lisa Johnson, a Senior Deputy Prosecutor with King County, works with police agencies around the county.

"It's an incredible challenge," she says. " And one that is becoming more significant all the time for law enforcement because in an age of decreasing resources and yet an explosion of digital evidence, they can't commit the kind of resources to the investigation of these types of cases."

Microsoft showed off a new device that could help. It's a specially designed, keychain-sized drive that pulls evidence directly off a computer.

This isn't a money-maker for Microsoft. The company offers it free to police around the world and encouraged cops at the conference to try it.

"Most importantly, tell us how we can make it better," said Microsoft General Counsel Brad Smith. "What new ideas should come to life this week so that when we get together a year or two from now, we have new tools and new success stories to which we can point."

Microsoft and law enforcement are building a new relationship -- a powerhouse team to combat crimes evolving and hiding in criminals' computers.