Arnold Schwarzenegger promised he'd be back, and by golly, the aging cyborg wasn't joshing! Terminator 3: Rise of the Machines debuted atop the box office with $44 million over the July 4 holiday weekend ($72.5 million since opening Tuesday). Although the well reviewed sequel opened at the low end of expectations — industry analysts predicted a $55 million bow —

T3 nonetheless represented a personal best for Schwarzenegger. Legally Blonde 2: Red, White &#038 Blonde snapped up the No. 2 spot with a so-so $22.9 million ($39.2 million since Wednesday). That marked Reese Witherspoon's second-best opening ever, behind Sweet Home Alabama's $35.6 million haul. Rounding out the top five: Charlie's Angels: Full Throttle (No. 3 and sliding with $14.2 million), Finding Nemo (No. 4 with $11 million) and The Hulk (No. 5 with $8.2 million). The weekend's big casualty? Sinbad: Legend of the Seven Seas. The sad little cartoon flopped, taking in $6.8 million for No. 6.