How to:Workflows Failed - User cannot found error

A workflow allows you to attach a business process to items in Microsoft SharePoint Foundation 2010. This process can control almost any aspect of an item in SharePoint Foundation 2010, including the life cycle of that item. For example, you could create a simple workflow that routes a document to a series of users for approval.
Workflows can be as simple or complex as your business processes require. You can create workflows that the user initiates, or workflows that SharePoint Foundation 2010 automatically initiate based on some event, such as when an item is created or changed.

Workflows Failed - User cannot found error : The workflows associated with site or specific list will get disappread along with history displyed in the site workflow page and workflows pages are throwing an error "user connot found".

Root cause : The Issue is primarly encountered due to the fact that the person who created the workflows using his/her NT account has been disabled in AD.

The problem arises due of the fact that the workflows were published by a user who is not known by SharePoint.

Solution :

The workflows which are got into trouble because above explained senario where the person who created it is no longer available in active directory, and also the sharepoint needed a valid account to validate the workflows. We need to re-publish the workflows using sharepoint designer ( 2010/2007 ).

Though the person who has created the workflow is no longer available, still we can access the workflows using sharepoint designer and re-publish them with a valid account existing in Active directory and having proper access to the site collection where we are publishing the site.

And to History of workflows which was vanished from the workflows settings page can be fetched from the

http://xxx.pfizer.com/sites/xxx/lists/Workflow%20History/AllItems.aspx