Willie Clark was arrested for a parole violation after his name surfaced in the investigation, police spokesman Sonny Jackson said.
"We're not calling him a suspect at this time," Jackson said.
Jackson said police have questioned more than 50 people since Williams was shot as he drove away from a New Year's Eve party at a nightclub in a stretch Hummer limousine.
An "associate" of Clark's also had been contacted but released, Jackson said.
"I hope he is a valuable individual that will help assist us," Jackson said of Clark. "I hope that he'll make a difference for us in solving this case."
In Fort Worth, Texas, Williams' family huddled around a home computer following his visitation service to watch the police news conference on the Internet.
Police won't say whether they know the motive for the slaying but have said there was an altercation at the club.
According to state criminal records, a man named Willie Clark with the same date of birth as the man arrested Friday has been arrested more than a dozen times since 1999, mostly for misdemeanors and failing to appear in court. In 2003, he pleaded guilty to motor vehicle theft, a felony, and reckless endangerment.
The record for Willie Clark listed three other dates of birth and several aliases.
Clark's arrest came a day after police officers found a 1998 Chevrolet Tahoe they believe could have been used in the drive-by shooting.
A person close to the investigation told The Associated Press the SUV is registered to Brian K. Hicks of Denver, who is jailed on unrelated drug and attempted murder charges. The person declined to be identified, because state law prohibits officials from identifying whom a vehicle is registered to.
Police would not comment on whether Hicks, 28, had agreed to be interviewed or whether gang involvement was suspected in Williams' death.
Hicks has been jailed since Nov. 9 on a charge of possessing drugs with intent to distribute. He also is accused of shooting at a woman who was later killed a week before she was to testify against him.