Howell, despite missing time because of fouls, made 10-of-12 shots as the 11th-seeded Wolfpack eliminated the sixth-seeded Aztecs (26-8).
North Carolina State (23-12) moves into the third round Sunday against Midwest Region No. 3-seeded Georgetown, which rolled over Belmont 74-59 Friday.
Howell had 12 points as the Wolfpack and San Diego State played even through 12 1/2 minutes. Another basket from Howell allowed North Carolina State to have a 33-29 lead at halftime.
The Aztecs got back to 57-54 but North Carolina State used an 8-2 spurt to create some distance and control things from there.
Howell's hot hand helped the Wolfpack to 57.4 percent (31-of-54) shooting. Lorenzo Brown added 17 points along with nine rebounds and seven assists. C.J. Leslie had 15 points and Scott Wood 10 for North Carolina State.
Jamaal Franklin popped in 23 points and Chase Tapley 19 to pace the Aztecs' attack.