Hi,
Follow the below steps when you cannot open default mail folder and get the error message stating: The file <drive>:\<path><file name>.pst could not be found.
This error may occur if Outlook is delivering mail to a personal folders (.pst) file, and any of the following conditions are true:
* Your personal folder file where Outlook delivers your mail is located on a server that is currently unavailable.
* Your personal folder file where Outlook delivers your mail is corrupted and Outlook can not open it.
Open a New Personal Folders File
If you want to open a new Personal Folders file, type a name for the new file in the "Create/Open Personal Folders File" dialog box and click Create.
Personal Folder File Located on a Network Server
Contact your system administrator to check the availability of the network server where your Personal Folder file is located.
Corrupted Personal Folder File
If you suspect that your personal folder file is corrupted, you may be able to recover the file using the Inbox Repair Tool.
To use the Inbox Repair tool, follow these steps:
1. Click Start, point to Find, and click Files Or Folders.
2. Type Scanpst.exe in the Named box and click Find Now.
3. In the list of found files, double-click the Scanpst.exe file.
4. Specify the name of the .pst file you want to repair, or click Browse to browse for the .pst file.
5. Click Start.
If there is an error, you have the option to make a backup of the file before attempting repairs.
The log file for the repair process has the same name as the .pst file, with a .log extension. So, if you repair a file named Mailbox.pst, the log file is named Mailbox.log.
Source: http://support.microsoft.com/kb/197267
