The Microsoft Exchange Information Store Service may not start automatically when the computer starts. If you try to manually start the Microsoft Exchange Information Store Service, you may receive the following error message:

Event 5000

Event Type: Error
Event Source: MSExchangeIS Event
Category: General
Event ID: 5000
Date: 14/4/2008
Time: 5:04:22 PM
User: N/A
Computer: EXFE01
Description: Unable to initialize the Microsoft Exchange Information Store service. Error 0×80040154.

This error happen if you have problem with SMTP component in IIS either missing or corrupted.

To solve this problem you have to Reinstall IIS and exchange 2003..It is easy one just follow MS KB326305

and everything will be fine.