今天安装dnn时发现asp.net加载报错，很多网友的建议是重装.net或者重装IIS，甚者都幸灾乐祸的说重装系统肯定能解决问题，不负责任的做法，有困难找google呵呵，最后尝试重新注册.net，结果就OK了，详细操作步骤见下：

1.Error:Failed to execute request because the App-Domain could not be created. Error: 0×80070005 Access is denied.

具体情况如下:
Server Application Unavailable

The web application you are attempting to access on this web server is currently unavailable. Please hit the “Refresh” button in your web browser to retry your request.

Administrator Note: An error message detailing the cause of this specific request failure can be found in the application event log of the web server. Please review this log entry to discover what caused this error to occur.

查看Event Viewer,看到的错误为:

Error:Failed to execute request because the App-Domain could not be created. Error: 0×80070005 Access is denied.

基本上，这个情况最可能发生在第一次执行 .Net work 2.0 ，原因不明，但底下的做法大致可以解决此问题：

1.开始-运行-cmd到命令行，并切换目录到 %SystemRoot%\Microsoft.Net\framework\(%SystemRoot% 视你 Windows 安装目录而定，一般是在 C:\Windows)

2.执行 “net stop w3svc” 终止 w3svc 服务
3.切换到下层目录 v2.0.5.xxx
4.执行 “aspnet_regiis.exe -ua” 解除 .Net 安装
5.重新安装 .Net 到 IIS 中 “aspnet_regiis.exe -i”
6.重新启动 w3svc “net start w3svc”.