"When you log on to a computer that is running Windows Server 2008 R2 or
Windows 7, the logon process stops responding and a blue swirl is shown on
the Welcome screen indefinitely."
"This issue occurs because of a race condition between the Windows Event Log
service and the Event Tracing for Windows (ETW) tracing functions. When the
race condition occurs, it causes a deadlock situation. This deadlock
situation then causes the Winlogon.exe process to become unresponsive.."
Other web sites suggest the prime cause is the many drivers
Win7 loads (and tucks away as if to discourage customization
for more speed.)
in my case (Gateway NV57H50u, regularly updated, 2 Gb RAM
added to total 4 Gb. I downloaded the hotfix from MS, but it said on
extraction "not for this computer."