I have only 1GB of space on my C drive but 3GB on a second partition. How can I tell Microsoft Office Outlook 2003 to put my .ost file for Cached Exchange mode on the E drive?
By default, Outlook places each Offline Folders (.ost) file and Personal Folders (.pst) file that it creates in the %userprofile%\Local Settings\Application Data\Microsoft\Outlook folder. You can either use a registry value to change that default location, or you can manually create a new profile and specify the .ost filename and folder.
See also, "Troubleshooter: .pst Files vs. .ost Files for Backups" and "Outlook: Displaying a Contacts Folder Other Than the Default."
To use a registry value to set the default path, open a registry editor and navigate to the HKEY_ CURRENT_USER\Software\ Microsoft\Office\11.0\Outlook key, create a new expandable string value named ForcePSTPath, and set it to the path to the folder in which you want Outlook to create .ost and .pst files. You can use environment variables, such as %userprofile%, to specify the path.
Alternatively, you can use the Custom Installation Wizard and Custom Maintenance Wizard tools from the Office 2003 Resource Kit to set the value of ForcePSTPath. The resource kit also contains the administrative template for Group Policy Editor (GPE), which you can use to mandate the value for ForcePSTPath as a policy setting in HKEY_CURRENT_USER\ Software\Policies\Microsoft\ Office\11.0\Outlook. The Microsoft article "You cannot specify a separate folder to store the .ost file when you use the ForcePSTPath value in Outlook 2003" explains how to get and use a hotfix that adds a new ForceOSTPath registry value to set the .ost file path separately from the .pst file path.
The manual method of changing the default location for .ost and .pst files requires you to set the .ost file location before you turn on Cached Exchange mode. Use the Control Panel Mail applet to create a new mail profile for an Exchange mailbox, but before you finalize the profile, clear the Use Cached Exchange mode check box. Open the new profile's properties again, choose E-mail Accounts, bring up the Exchange account settings, and choose More Settings. On the Advanced tab, click Offline Folder File Settings. You should see a dialog box in which you can set the location of the .ost file. Upon request, confirm that you want to create the new .ost file. Return to the settings for the Exchange account, select the Use Cached Exchange mode check box, then click OK to save the profile changes.