Microsoft postponed the roll-out of the Windows 7 beta on Friday, citing "very heavy traffic" on its Web site.
The company did not offer a new schedule for delivering the beta of its newest operating system.
"Due to very heavy traffic we're seeing as a result of interest in the Windows 7 Beta, we are adding some additional infrastructure support to Microsoft.com properties before we post the public Beta today," a spokeswoman said in an instant message reply to earlier questions about the Microsoft.com's performance.
"We want to ensure customers have the best possible experience when downloading the Beta."
On Wednesday, CEO Steve Ballmer promised that the beta would be released to the general public Friday.
Later, a company spokeswoman said that Microsoft would post the beta Friday at noon PST.
Early Friday, however, several Microsoft domains, including the main page and the designated download site, were overwhelmed by users eager to grab the beta.
Although those URLs were later revived, attempts by Computerworld and others to download Windows 7 from a TechNet page aimed at IT professionals have been stymied for several hours.
Users who have tried to download the beta have been greeted with messages such as "Server is too busy" and "This site is currently experiencing technical difficulties, please check back in the next business day."
The Microsoft spokeswoman did not know when users could expect to download the beta. "No ETA at this point," she said via a follow-up instant message.
Although Microsoft has said it would cap the number of Windows 7 beta activation keys at 2.5 million - perhaps one of the reasons users felt a sense of urgency Friday about getting the download - it is not expected to yank the download after that mark is reached.
Users unable to obtain an activation key in the initial rush will still be able to download and install the beta, then run it under the operating system's 30-day trial.
By using the same "slmgr -rearm" command that gained notoriety after Windows Vista 's debut, users can extend that trial period to a total of 120 days.
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