Usually a damaged Microsoft Outlook PST file can be repaired by using a mirror PST file as an example and adjusting the original file to match it. However, sometimes malware and other virus attacks can be so insidious as to block overwriting of the contaminated file portions with the fresh original content. In these situations the only solution is to extract all of the core information that being your messages and customizations along with scheduling and calendar functions. This information can then be installed into a new PST file and create a new workable Microsoft Outlook inbox.
When this solution fails which indeed it can if the virus attack is pervasive enough, the remaining solution is to use the PST repair program as a file reader. Most of the better corrupted PST repair programs include the option of being able to open the PST file and at the very least examine its contents.