Windows 11 and C21

C21 is compatible with Windows 11 but NOT version 24H2. This version of Windows 11 causes a harmless but persistent warning message when logging in to C21 or switching companies that we are not able to prevent. Please stop any automatic Microsoft updates. If you have recently updated your Windows to 24H2, roll back the update as soon as possible. Please follow these instructions:

Make sure you have the following items:

  • Actian PSQL License Key
  • Installer for Actian PSQL for your current version
  • Backup of your computer and C21 Data folder
  1. Deauthorize your PSQL license key first by going to Start/All Apps/Actian.../License Administrator.
  2. Then click on the key and deauthorize.
  3. At your Windows Search bar, type Uninstall to find the Add or Remove Apps control menu. Look for Actian and click Uninstall.
  4. Run through the Wizard to uninstall Actian PSQL.

Follow these instructions to roll back 24H2: 
1. Press Windows + I
2. Go to System/Recovery
3. Find "Go Back" and click it. 

Once this is done, re-install PSQL:

  1. Run the PSQL installation wizard and select Workgroup and the Run as a Service option.
  2. Copy and paste your key after installation and authorize.

After this procedure, check to see if you still get the warning message. If you are successful and you have workstations, you do the same procedure on any workstations.

If it has been more than 10 days since you installed the Windows 11 24H2 update, you will need to do a manual re-install. We recommend you hire an IT person to assist you with this procedure.

1. Download Windows 11 23H2 ISO

  • Go to: UUP Dump
  • Select:
    • Windows 11
    • Build: 22631.xxx (this is 23H2)
    • Choose your edition: Home, Pro, etc.
  • Click Download and convert to ISO

(Microsoft’s own site no longer provides 23H2 ISOs after 24H2 is out, hence these alternatives.)

2. Create a Bootable USB

  • Download Rufus
  • Insert your USB
  • Open Rufus → Select the ISO → Select USB drive
  • IMPORTANT: Under Image option, choose “Standard Windows installation” (not “Windows To Go”)
  • Click Start → Wait for it to complete

3. Back Up Your Files

  • Use OneDrive, Google Drive, or an external drive
  • This process will erase your system drive (C:)

4. Boot from USB

  • Restart your PC and enter BIOS (usually F12, F2, ESC, or DEL)
  • Select USB boot device
  • When Windows setup begins:
    • Choose Custom: Install Windows only (advanced)
    • Select your primary drive (usually labeled as “Drive 0”) and delete the partitions if you want a fresh install

5. Install Windows 11 23H2

  • Continue setup
  • Reconnect to Wi-Fi when prompted
  • Skip Microsoft Account sign-in (optional using Shift+F10 and bypass scripts if desired)

Post-Install Tips

  • Install your drivers (Windows Update should handle most)
  • Reinstall software and restore your files
  • Block 24H2 updates

Please note that Actian (PSQL) no longer supports version 13 or earlier. If you have v12 or v13, we recommend you do not rename your computer as Actian will think you have installed on another computer. If your computer crashes and you are unable to deauthorize your key, they will not reactivate it for you and will force you to purchase a new license.

Please not that you must have a Pervasive license of Version 12 or higher to run on Windows 10 or later and Windows Server 2019 or later. Your license will be noted in the Help/About window of C21 menu. If you would like to upgrade your license, please contact us at inquiry@c21accountingsoftware.com.