The Belgian next faces fourth seed Elena Dementieva, who overcame a terrible start before ousting Serbian teenager Ana Ivanovic 2-6, 6-4, 6-2 to reach the last four in Indian Wells.
In the men's draw, two-time champion Roger Federer strolled into the semi-finals with a 6-2, 6-3 win over sixth seed Ivan Ljubicic. Federer will face a resurgent Paradorn Srichaphan of Thailand, who downed Finland's Jarkko Nieminen 7-6, 3-6, 7-5 in two hours and 41 minutes to reach his first Masters Series semi-final since 2003.
Former world No 1 Henin-Hardenne, who has yet to drop a set in four matches, had few problems with the speedy Dulko, who she had never played before.
The Argentine tried to wear her opponent down by counter attacking, but the Belgian had far too much power and a few too many tricks up her sleeve.
"When you've never played someone, you don't know really what to expect," Henin-Hardenne said. "I know she had nothing to lose, so I knew it was going to be a tough match. But I think I controlled the match, even if my attitude was a bit negative sometimes."
Federer stifled Ljubicic from the outset to record his sixth straight win over the Croatian. The Swiss had little trouble in frustrating Ljubicic with his sublime placements of the ball.
"I consider myself a top-five player but that doesn't mean I'm close to Roger," world No 6 Ljubicic said.