In-Place Upgrade from Windows Server 2003 to Windows Server 2025 with Active Directory Schema Update

With the release of Windows Server 2025, many organizations are looking to modernize their aging infrastructure. However, if you’re running a Domain Controller (DC) on Windows Server 2003, be aware that direct in-place upgrades to Windows Server 2025 are not supported.

This article outlines a multi-step upgrade path to bring your AD environment from Windows Server 2003 to Windows Server 2025, ensuring both functional continuity and schema compatibility.

🚨 Important Notes Before You Begin

No direct in-place upgrade from 2003 to 2025 is supported. You’ll need to upgrade through at least one intermediate OS, such as:
- Windows Server 2003 → 2008 R2 → 2012 R2 → 2019 → 2025
This article focuses on schema updates and Domain Controller modernization.
In-place upgrades should only be done if absolutely necessary; Microsoft strongly recommends migrating to newer servers and promoting them instead.

🧰 Prerequisites

A complete system and Active Directory backup of the 2003 server.
Functional and healthy AD environment (test using dcdiag and netdiag).
The Windows Server 2003 DC is running SP2.
Upgrade media for intermediate versions (2008 R2, 2012 R2, 2019, 2025).
Sufficient hardware to meet modern OS requirements.
FSMO roles transferred, or a strategy to migrate them properly.

🔄 Step-by-Step Upgrade Path

You must first upgrade the schema and then upgrade the DCs through intermediate versions.

🧱 Step 1: Upgrade Active Directory Schema for Windows Server 2008 R2

On your Windows Server 2003 Schema Master:

Insert the Windows Server 2008 R2 DVD.
Run: adprep32 /forestprep adprep32 /domainprep

adprep32 is used on 32-bit servers. If on 64-bit, use adprep.

Wait for confirmation messages and ensure replication is complete.

💻 Step 2: In-Place Upgrade to Windows Server 2008 R2

Boot into Windows Server 2003.
Run setup from Windows Server 2008 R2 DVD.
Choose Upgrade option.
Complete the upgrade wizard and allow the server to reboot.

Test domain functionality using:

dcdiag
repadmin /replsummary

🪜 Repeat Upgrade Process

Repeat schema upgrades and OS upgrades through these steps:

👉 2008 R2 to 2012 R2

Run adprep /forestprep and adprep /domainprep from 2012 R2 media.
Then do in-place upgrade to Windows Server 2012 R2.

👉 2012 R2 to 2019

Again, run adprep /forestprep and adprep /domainprep from 2019 media.
Perform in-place upgrade to Windows Server 2019.

👉 2019 to 2025

Run adprep /forestprep and adprep /domainprep from Windows Server 2025 media.
Finally, do in-place upgrade to Windows Server 2025.

🔍 Schema Version Reference

Each schema update bumps the objectVersion:

Windows Server	Schema Version
2003	30
2008 R2	47
2012 R2	69
2016	87
2019	88
2025	TBD (expected > 88)

Check schema version using:

reg query "HKLM\SYSTEM\CurrentControlSet\Services\NTDS\Parameters" /v "Schema Version"

Or:

ldifde -f export.txt -d "cn=schema,cn=configuration,dc=domain,dc=com" -l objectVersion

✅ Post-Upgrade Validation

After reaching Windows Server 2025:

Run dcdiag and repadmin /showrepl.
Check DNS and SYSVOL replication.
Confirm that Group Policies, login scripts, and replication function as expected.
Optionally raise the domain and forest functional levels using Active Directory Domains and Trusts.

💡 Migration Tip

Instead of in-place upgrades, a better long-term approach is:

Stand up a new Windows Server 2025 machine.
Promote it to a DC using dcpromo (or Server Manager).
Transfer FSMO roles.
Demote and decommission the old Windows Server 2003 DCs.

This method is cleaner, safer, and future-proof.

Conclusion

While it’s technically possible to upgrade from Windows Server 2003 to 2025 via in-place upgrades and schema updates, the process is multi-step and risky. Whenever feasible, build a modern AD environment on fresh hardware or VMs, then migrate.

If you’re looking for assistance in planning, executing, or automating Active Directory modernization, contact our team to get expert help tailored to your environment.

Would you like this article formatted for WordPress (with proper headings and shortcodes), a downloadable PDF version, or turned into a step-by-step video script?