It looks as if a key Microsoft partner jumped the gun and announced the retail availability of Windows Vista Service Pack 1 (SP1) a little early. What's more, it may have let the cat out of the bag for online availability as well.

Amazon.com announced on its Web site – inadvertently or not – that Vista SP1 will be available for download Tuesday, March 18 for some customers. The disclosure came as Amazon was promoting the pending availability of SP1.

"You can pre-order Windows Vista with SP1 or Windows Vista with SP1 Upgrades now to get SP1 included in the box. Or buy the current versions of Windows Vista now, then update to SP1 online--free of charge--when the new versions are released on March, 18, 2008," according to a statement on Amazon's site.

Monday, Microsoft released a brief statement that appears to verify Amazon's statement.

"[W]hen looking at Amazon's site, you will see separate listings – one for pre-orders of Windows Vista with SP1 integrated, and the current version of Windows Vista, which does not include SP1, and can be purchased now and easily updated with SP1 online beginning March 18," a Microsoft spokesperson said in an e-mailed statement.

However, Microsoft hedged when asked when precisely SP1 will be available for customers who already have Vista. "Microsoft is still on track to deliver Windows Vista SP1 RTW [release to Web] in mid-March," Monday's statement said.

When reminded that mid-March is already here and nearly passed, the spokesperson did not respond further.

SP1 exited beta testing and went to manufacturing in early February. At that time, the company announced that delivery of the update would be staggered.

"In mid-March, we will release Windows Vista SP1 to Windows Update (in English, French, Spanish, German and Japanese) and to the download center on microsoft.com. Customers who visit Windows Update can choose to install Service Pack 1," said a blog posting at the time by Mike Nash, corporate vice president of Windows product management. That includes PC OEMs, retail packaged product, and download sites.

Meanwhile, a Malaysian news site claims to have gotten a copy of the actual schedule for SP1's availability. The site – TechArp.com – said that Tuesday, March 18, users who have Vista will be able to manually download the service pack from Microsoft's Download Center. On April 18, the site claims, Vista SP1 will be available for automatic download via Windows Update.