Microsoft 365 Installation Problems

How to Install Microsoft 365 on D Drive and Move Outlook Data

Elise Williams Oct 9, 2026 870 views

Question details

The user wants to install Microsoft 365 on the D: drive and store a large Outlook data file (over 65 GB) there to save system drive space on a new laptop.

How to Install Microsoft 365 on the D Drive and Move Outlook Data Files

Product: Microsoft 365, Outlook
Device & OS: Windows
Scenario: Setting up a newly purchased laptop with limited C: drive space and a massive Outlook mailbox that requires more than 65 GB of storage.
Observed behavior: Microsoft 365 desktop applications automatically install on the Windows system drive without an option to change the path, and Outlook creates its data files on the C: drive by default.

Before you start

Verify that your D: drive is an internal, locally attached storage drive (preferably an SSD) with at least 100 GB of free space before redirecting heavy system applications or large Outlook data files.

Solution 1Recommended

Keep Microsoft 365 on the System Drive and Relocate the OST File via Registry

Because Microsoft 365 applications must remain on the system drive, the best approach is to leave the apps on the C: drive and use a registry key to force Outlook to store your large data files on the D: drive.

Microsoft does not provide a built-in installer option to change the default installation path for Microsoft 365 applications. Attempting to force the installation to another drive can cause update failures and system instability. Instead, you should configure a new Outlook profile and dictate the OST storage path before syncing your mailbox.

Open the Registry Editor

Press the Windows Key + R to open the Run dialog, type 'regedit', and press Enter. Click 'Yes' if prompted by User Account Control.

Navigate to the Outlook Path

Go to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook (replace 16.0 with your version number if you are using an older Office version).

Create the ForceOSTPath String

Right-click an empty space in the right pane, select 'New', then 'Expandable String Value'. Name it 'ForceOSTPath'.

Set the New Drive Location

Double-click 'ForceOSTPath' and enter your desired D: drive folder path (e.g., D:\OutlookData) into the Value data box. Click OK and close the Registry Editor.

Create a New Outlook Profile

Open the Windows Control Panel, search for 'Mail', and open the Mail setup. Click 'Show Profiles', add a new profile, and set up your email account. Outlook will now generate the new OST file on the D: drive.

Keep Microsoft 365 on the System Drive and Relocate the OST File via Registry

Registry Modification Warning: Modifying the registry can cause system issues if done incorrectly. It is highly recommended to back up your registry before proceeding with this method.

Solution 2

Move Existing Outlook Data Using Symbolic Links

If you have already configured Outlook and simply want to move the existing data file to the D: drive without messing with registry keys or creating a new profile.

Free Microsoft Office alternative

Try WPS Office for a Lightweight, Customizable Office Experience

If you are struggling with Microsoft 365's rigid installation requirements and massive storage footprint, consider switching to WPS Office. It provides a lightweight, flexible installation process that allows you to choose your preferred drive, saving valuable system space while maintaining full compatibility with Microsoft formats.

1. Download the Installer: Visit the official WPS Office website and download the free installation package.
2. Run Setup and Choose Path: Launch the installer, click on 'Custom Options' or 'Settings' in the setup wizard, and select your preferred folder on the D: drive.
3. Complete Installation: Click 'Install' to finish the setup and enjoy your lightweight, storage-friendly office suite.

Requires significantly less storage space on your system drive compared to Microsoft 365.Allows you to easily select a custom installation path (like the D: drive) during setup.Fully compatible with Microsoft Word, Excel, and PowerPoint file formats (.docx, .xlsx, .pptx).Free to use with a familiar, intuitive user interface for seamless migration.

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Frequently Asked Questions

Can I install Microsoft 365 on a drive other than C:?

No, Microsoft 365 applications automatically install on the drive where Windows is installed (usually the C: drive). Microsoft does not provide a built-in option to change this default installation path for standard consumer or enterprise desktop apps.

What happens if my Outlook OST file exceeds 50 GB?

By default, Outlook limits the OST file size to 50 GB. If your mailbox data exceeds this (e.g., 65 GB), you must increase the maximum size limit using the 'MaxLargeFileSize' and 'WarnLargeFileSize' registry keys; otherwise, Outlook will display error messages and refuse to sync new emails.

Will moving my Outlook data to the D: drive affect performance?

It depends on the hardware of your D: drive. If the D: drive is a fast internal SSD, performance will remain excellent. However, if it is a slower mechanical Hard Disk Drive (HDD) or an external USB drive, Outlook may run noticeably slower, especially when searching or indexing a massive 65 GB data file.

Installation & Activation