Unable to load all ISAPI filters for the site/service. So start abort error resolution

The Service Unavailable error occurs when the Web site is accessed, and the following error message appears in the System log: Unable to load all ISAPI filters for the site/service.

The following is a collection of related cause analysis and resolution, please read it carefully.

Service Unavailable Solution
Why is the service unavailable?
First, if the "Service unavailable" prompts, a few refreshing and can be accessed.
This occurs because your Web site exceeds the IIS limit, because 2003 of the operating system does not prompt IIS as "too many links", but prompts "Service unavailable", as the 2000 system prompts. This situation occurs because the Web site exceeds the system resource constraints, mainly because the program consumes too much resources. For example, the same 100-person online forum, the Forum's resources are the PW forum accounted for more than 10 times times the resources; In addition, some dead loop program, or not optimized program will occupy too much system resources, and system resources are obviously limited. However, the WINDOWS2003 operating system, the Web site is running in a separate process, will not affect each other.
If a Web site has too many programs or too many errors, the system log prompts: "Application pool ' xxx" is automatically disabled because of a series of errors in the process serving the application pool, or because the application pool ' xxx ' exceeds its job restriction setting. At this point, visit this site will be prompted: Service unavailable. The general system will return to normal in about 30 seconds, more than a few times can be normal access to refresh. For more information, see the Help and Support Center in http://go.microsoft.com/fwlink/events.asp. At this point, visit this site will be prompted: Service unavailable. The general system will return to normal in about 30 seconds, more than a few times can be normal access to refresh.
In addition, if your site currently has too many visitors, more than the system's IIS connection limit, there will be a service unavailable (Win2K host too many connections will be prompted: Too many connections, please try again later While the Win2003 host just directly prompts: Service unavailable)

Two, do not restrict IIS connection, or encounter service unavailable

Users who are generally using Windows 2003 IIS 6 may have a normal system for this problem, and suddenly a website can't be opened.
Tip: Service unavailable But this site does not limit the number of IIS connections. Then immediately affect other sites, less than a while, other sites are all turned into Service unavailable
What's the reason?
We can know after analysis, or MS's old problem. The access engine was. With the server doctor's file Doctor repair, when you view the fix results, you will find some files that caused the access engine to "catastrophic failure" and "not set object references to instances of objects." The system will not return to normal until the file doctor fixes it.

Third, when browsing a Windows SharePoint Services Web site, prompt: Service unavailable

This problem may occur if the application pool for the virtual server is not configured correctly in Microsoft Internet information Services (IIS) 6.0. This problem may occur when one or more of the following conditions are present: A. The application pool is not running. B. The password used by the application pool account is incorrect. C. The application pool account is not a public member of the two groups of IIS_WPG and STS_WPG on the server.
Solution
To resolve this issue, follow these steps: 1. Verify that the application pool has been configured for the virtual server. The default application pool is MSSharePointPortalAppPool.
Follow these steps to determine which application pool the virtual server is using.
A. Click Start, point to Administrative Tools, and then click Internet Information Services (IIS) Manager.
B. Expand ServerName, expand Web Sites, right-click the virtual server, and then click Properties.
C. Click the Home Directory tab. The application pool configured for the virtual server is listed in the Application pool box.
D. Click OK.

2. Verify that the password used by the application pool account is correct. IIS does not automatically poll for password changes in the Active Directory directory service. If the application pool account is a domain account and its password has expired, you may receive the error message that is described in the "Symptoms" section of this article after you reassign a new password for this account.

Follow these steps to verify that the password used by the application pool account is correct:
A. In Internet Information Services (IIS) Manager, expand Application Pools.
B. Right-click the application pool configured for the virtual server (for example, right-click MSSharePointPortalAppPool), and then click Properties.
C. Click the Identification tab.
D. In the Password box, type the password for the application pool account that is listed in the User name box, and then click OK.
E. In the Confirm Password dialog box, type your password again, and then click OK.

3. Verify that the application pool account is a member of the IIS_WPG and STS_WPG groups on the server.

Choose one of the following methods, depending on your situation.

A. In the case where SharePoint Portal server is installed on a member server: 1. Click Start, point to Administrative Tools, and then click Computer Management.
2. Expand Local Users and groups, and then expand users.
3. Right-click the account used by the application pool for the virtual server, and then click Properties.
4. Click the members Belong tab.

Verify that both IIS_WPG and STS_WPG appear in the member belongs list. If either of these are not listed or both are not listed, add the IIS_WPG group, STS_WPG group, or these two groups to the list as appropriate.

B. In the case of a SharePoint Portal Server installed on a domain controller:

1. Start Active Directory users and computers.
2. Expand "Users".
3. Right-click the account used by the application pool for the virtual server, and then click Properties.
4. Click the members Belong tab.

Verify that both IIS_WPG and STS_WPG appear in the member belongs list. If either of these are not listed or both are not listed, add the IIS_WPG group, STS_WPG group, or these two groups to the list as appropriate.

4. Restart IIS to recycle the application pool:

A. In Internet Information Services (IIS) Manager, right-click ServerName, point to All Tasks, and then click Restart IIS.
B. Click Restart Internet Information Services on ServerName, and then click OK. The above questions from the online collection may be encountered, I found the problem:

Four. May be installed some software, the relevant services to remove the problem: has been normal, installed a anti-theft chain system and Uninstall, restart the machine, appear Service Unavailable Event Viewer has: all ISAPI filters that cannot load the site/service. So start abort. The application pool is turned off after IIS is started, but can be started manually, but the problem persists. Workaround: Restart IIS, create a new Web site, application pool. Result: Open iis--> View the properties of the total Web site--->isapi filter--> remove items with down Red Arrows--> restart Iis-->ok