In view of this problem is difficult to solve the occurrence and significance of the solution of example, idiopathic at home.
Questions raised: Silverlight can not be prompted to download and display, in Firefox in IE normal
system environment: Vista, IE7
corresponding version: . RC 1.0, 1.0 RTW, 1.1 Alpha Refresh Aug./Sept
describe the phenomenon: visit a page that contains Silverlight, tips Download and install Silverlight, after installing the installation was successful, refresh the page, still need to be prompted to download and install; however, open Firefox to access the page was able to be displayed properly. Note: In Vista installation to use Administrator privileges (the shortcut menu, Run as administrator)
resolution process:
try to uninstall reinstall, reboot, etc., can not be resolved. The problem appears to be very simple, but the solution can not start up somewhat. First thought is the ability to get some information or Debug Log, but had not found; the reference to some of the information in the prompt Silverlight Products Xiaoying, using the following method (after a lot of problem can be view):
1, download the latest Microsoft Process Monitor .
2, and open the page start IE contains a Silverlight application.
3, open Process Monitor, selection filter Process Name is iexplore.exe (FIG. 1). 
4, refresh the page containing the aforementioned Silverlight program.
5, then you will find iexplore.exe will attempt to access HKCR \ AgControl.AgControl, but the access result is ACCESS DENIED (Figure 2). The problem is here! 
6, discovered the problem and solve it is not so simple. Open the Registry, try to modify HKCR \ AgControl.AgControl of authority? Access is denied, in any case not allow modifications.
7, check the information, finally found, is the authority in question HKCR (privileged user list is empty, and not the same as other machines) which led to the installation of AgControl.AgControl a problem, that was it! Find a normal Vista registry keys (thank Felix ), referring to what their machines HKCR set permissions (Figure 3). 
8, uninstall Silverlight, reinstall, OK, get!
Conclusion: looks like a problem Silverlight installer, the registry HKCR is actually a problem in itself. Process Monitor tool is a good debugger.
Reference: Currently online reference materials, little Silverlight, Silverlight only official Forum there are some references:
http://silverlight.net/forums/p/600/11562.aspx
http://silverlight.net/forums/t/ 3391.aspx
Reproduced in: https: //www.cnblogs.com/arielyang/archive/2007/09/12/891203.html