How to copy a .pst file to a USB stick?

Aisling Judge 50 Reputation points
2026-07-01T16:32:25.5033333+00:00

When I try to copy my Outlook.pst file to a USB stick I get an error saying the file is too big for the file system. How can I overcome this problem?

Outlook | Windows | Classic Outlook for Windows | For home
Answer accepted by question author
Marcin Policht 109.3K Reputation points MVP Volunteer Moderator
2026-07-01T16:42:10.86+00:00

That error usually means the USB stick is formatted with the FAT32 file system, which has a maximum single-file size limit of 4 GB. Outlook PST files are often much larger than that.

The simplest fix is to reformat the USB drive as exFAT or NTFS, both of which support large files. Before formatting, copy any important files off the USB stick because formatting erases everything.

In Windows Explorer, right-click the USB drive, choose Format, then select either exFAT (best for compatibility with Windows and Mac) or NTFS (Windows-focused). Leave the allocation size as default and start the format.

After formatting completes, try copying the PST file again and it should work normally.

If you cannot reformat the USB stick, another option is to compress or split the PST file into smaller parts using tools like 7-Zip or WinRAR.

If the above response helps answer your question, remember to "Accept Answer" so that others in the community facing similar issues can easily find the solution. Your contribution is highly appreciated.

hth

Marcin

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  1. Ritu Arora 80 Reputation points
    2026-07-01T16:45:31.95+00:00

    Hi Aisling, your USB stick is formatted as FAT32 which has a 4GB file size limit. Format the USB to exFAT (right-click USB in File Explorer → Format → select exFAT) and then copy the .pst file again.

    Ritu Arora, MCT

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