At 6AM PDT, when Windows 7 Release Candidate downloads were officially made available for MSDN and TechNet subscribers, after 20 minutes or so of smooth downloads, both sites began bogging down, and the situation deteriorated rapidly as the minutes passed. For several hours after the official launch, most subscribers who tried to log on found themselves unable to reach the download pages. The glitch was caused by a SQL Server database that reached excessive fragmentation levels because of the tremendous surge of queries. The following graphic is from an internal Microsoft document explaining what happened. The blue line indicates percentage of processor usage, which is directly tied to fragmentation of the SQL Server database, reports Ed Bott.