Today I'm happy to install Visual Studio 2008 Service Pack 1. The installation is successful.
But after that, my IE6(SP2) cannot work normally, error "Not enough storage is available to complete this operation" happens when:

1) in Javascript, call window.showModalDialog, and in the opened page, access navigator.appCodeName, navigator.appVersion or navigator.userAgent
2) click IE Help menu -> About

After some searching and studying, I finally find some hints:
http://www.technologyquestions.com/technology/windows-xp/205292-windows-update-problem.html

The reason is User Agent too long! VS2008 SP1 add all CLR versions to user agent, and obviously, IE doesn't handle this correctly. See this picture

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\5.0\User Agent\Post Platform]
So it is easy to work around: I don't need .Net 3.0, just remove them and IE resume working.