When Microsoft launches a new platform, it hires major rock acts to climb onstage with Bill Gates and stoke a media frenzy. HD DVD backers could barely get their product to stores on time, let alone strike up a band for the debut.

Universal and Warner homevid struggled to get three out of four launch titles into stores last week: Warner missed the April 18 street date for “Million Dollar Baby,” while tardy shipments of “Serenity,” U’s debut title, left some retailers at a loss.

The studios left the promotion to the stores themselves, a debatable strategy that led to predictable confusion, with at least one clerk advising an eager HD DVD customer that “it wasn’t out yet.”

Despite these glitches, reps say they’re pleased the format made it out of the gate — and ahead of rival high-def format Blu-ray. Sony will begin releasing its high-def discs May 23, a full month before the first players hit stores.