Windows Indexing Service allows for faster file searching while providing better performance. In context of Outlook PST, the service may cause several errors if it finds the PST corrupted. The Windows Indexing Service can index all PST objects, which include e-mails, calendar entries, and notes, etc. But if it starts indexing a corrupted PST (which needs PST Repair), it prompts errors of incomplete operation.

Here is an example that will elucidate such situations. In a scenario, wherein a Windows user uses Windows Indexing Service to index his/her Outlook PST file, an attempt to search an Outlook object may result in certain errors, such as:

"Instant Search encountered a problem while trying to display search results. Modifying your query may resolve this problem."

This error dialog box consists of no option to escape, but OK. When you click OK, this prompts another error, which reads as:

"Search results may be incomplete because items are still being indexed. Click here for more details"

On clicking error details option, you get the below error info:

"Outlook is currently indexing your items. Search results may be incomplete because items are still being indexed."

Apart from the error statement, you can also see a number of items to be indexed in PST.

Such issues are more frequent due to PST corruption. However, incomplete PST indexing can also result in similar kind of behavior. Therefore, you should look if PST is being indexed before actually looking for PST Repair solutions. To do so, click Options under Tools menu and select Search Options. If it shows that PST is being indexed, let the process to get completed.

In other cases, you would require to Repair PST. For this, you can run Inbox Repair Tool, which is a built-in repair tool for Outlook PST. Search for 'scanpst.exe' file in your Windows computer and double-click to launch the tool.

If the Inbox Repair Tool doesn't work, you need to use a third-party Outlook PST Recovery tool to Repair PST. These are downloadable applications available from data recovery manufacturers. You can buy these software and run them to repair your PST, corrupted because of any reason. These tools are highly effective and user-friendly.