How to Fix the “WDCSAM64_Prewin8.sys” Driver Compatibility Error in Windows 11

The safest fix is to update or remove the old Western Digital driver that Windows 11 flags as WDCSAM64_Prewin8.sys. This error usually appears when Memory integrity in Core isolation refuses to turn on because an outdated storage driver is still installed. Microsoft says incompatible drivers can block Memory integrity, even if the related device is no longer connected [source: Microsoft].

TLDR: The user should first update Western Digital software, then remove old WD apps, then delete the stale driver package if Windows still complains. For example, a PC that once used a WD My Passport drive may keep the old WDCSAM64_Prewin8.sys driver for years, even after the drive is gone. In many cases, the fix takes under 10 minutes, but driver cleanup can take longer if several old oemXX.inf packages are present. The main goal is simple: remove the bad driver without turning off Windows 11 security features for good.

What Is WDCSAM64_Prewin8.sys?

WDCSAM64_Prewin8.sys is linked to older Western Digital storage software and drivers. It is often tied to WD external drives, WD SES drivers, WD SmartWare, WD Discovery, or WD Drive Utilities.

The annoying part is that Windows 11 may complain about it even when no Western Digital drive is plugged in. The driver can sit in the Windows driver store and still block Core isolation. That feels ridiculous, but it happens a lot.

The error usually says that Memory integrity cannot be enabled because of an incompatible driver. Windows may show the driver name, its publisher, and sometimes an INF file name. That INF file matters because it helps identify the exact package that needs removal.

Fix 1: Update Western Digital Software First

The user should start with the least risky fix. If Western Digital tools are still installed, they should be updated before anything is removed.

Open Settings.
Go to Apps > Installed apps.
Search for Western Digital, WD Discovery, WD Drive Utilities, or WD SmartWare.
Open the WD app and check for updates, if that option exists.
Restart the PC.
Go back to Windows Security and try Memory integrity again.

If the updated driver is accepted by Windows 11, the job is done. If not, the old package probably needs to be removed.

Fix 2: Uninstall Old WD Apps

If the user no longer needs WD tools, removing them is often the cleanest move. External drives usually work without old bundled utilities.

Open Settings.
Click Apps.
Choose Installed apps.
Uninstall old WD programs one by one.
Restart Windows 11.

After the restart, the user should open Windows Security > Device security > Core isolation details. If Memory integrity turns on, the issue is fixed.

The catch is that an uninstaller may remove the app but leave the driver behind. That is when Device Manager or Command Prompt becomes necessary.

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Fix 3: Remove the Driver in Device Manager

Device Manager can remove the driver if Windows still detects the related device.

Right-click Start.
Select Device Manager.
Click View > Show hidden devices.
Expand Disk drives, Storage controllers, and Universal Serial Bus controllers.
Look for old Western Digital entries.
Right-click the device and choose Uninstall device.
If shown, tick Delete the driver software for this device.
Restart the PC.

This method is safer than deleting files by hand. It also lets Windows clean related registry entries.

Fix 4: Use PnPUtil to Remove the Stale Driver Package

If the error remains, the old driver may still be inside the Windows driver store. The user can remove it with PnPUtil.

First, an elevated Command Prompt is needed:

Search for cmd.
Right-click Command Prompt.
Select Run as administrator.

Then run:

pnputil /enum-drivers

The user should look for entries that mention Western Digital, WD, or the driver name WDCSAM64_Prewin8.sys. Windows will show a published name such as oem42.inf. The number will vary.

Once the correct INF file is found, the user can run:

pnputil /delete-driver oem42.inf /uninstall /force

The user must replace oem42.inf with the actual INF name shown on that PC. This part needs care. Removing the wrong driver can break another device. Honestly, it feels like Windows should make this clearer instead of forcing people to hunt through a long driver list.

After removal, the PC should be restarted. Then Memory integrity should be turned on again.

Fix 5: Avoid Deleting the SYS File Unless There Is No Choice

Some users try to delete C:\Windows\System32\drivers\WDCSAM64_Prewin8.sys by hand. That should be a last resort. A manual file delete can leave broken driver records behind.

If a technician chooses this route, a restore point should be created first. Safe Mode may be required. Still, removing the driver package with PnPUtil is usually the better fix.

Should Memory Integrity Be Turned Off?

Turning off Memory integrity will hide the warning, but it does not fix the driver. It also lowers protection against some attacks. The better plan is to update or remove the old Western Digital driver, then keep Memory integrity enabled.

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