Some customers running PicoHarp 300, HydraHarp 400, or MicroTime 200 on Windows 10/11 have found that the instrument driver (pqusb64.sys) fails to load once Windows Core Isolation — specifically the Memory Integrity (HVCI) feature — is enabled. This is common on newer PCs, where Memory Integrity is often turned on by default, and on managed lab/IT machines where security policies enable it.
Symptoms
- The acquisition software (PHR300/UniHarp, HydraHarp software, SymPhoTime 64 / MicroTime 200) cannot establish communication with the instrument, even though it is powered on and connected via USB.
- Device Manager shows the device with a driver error, commonly Code 27 or "{Bad Image}": "%hs is either not designed to run on Windows or it contains an error..."
- Windows Security may list the PicoQuant USB driver under Core isolation > Memory integrity > Incompatible drivers.
- The same hardware and software work fine on an older PC/OS where Memory Integrity is off or unavailable (e.g. Windows 7/10 without HVCI), which is a good way to confirm this is the cause.
Root cause
The pqusb64.sys driver used by PicoHarp 300, HydraHarp 400, and MicroTime 200 predates Windows' hypervisor-protected code integrity requirements and is blocked from loading when Memory Integrity is active. Newer instruments (MultiHarp, PicoHarp 330, HydraHarp 500) use a different driver and are not affected by this issue.
Fix: updated driver (recommended)
An updated version of the driver that is compatible with Core Isolation / Memory Integrity is now available:
- Release notes: readme.txt
- Download: driver_PQUSB64_core-isolation_fixed.zip
Installation:
- Unpack the zip file to a location of your choice.
- Open Device Manager, locate the device (it may show a warning icon or be listed under "Other devices"), right-click it and choose Update driver.
- Choose "Browse my computer for drivers" and point it to the folder where you unpacked the zip file.
- Complete the update and, if prompted, restart the PC.
With this driver installed, Memory Integrity can remain enabled — you do not need to lower your system's security posture to use the instrument.
Workaround (if you can't update the driver right away)
Before the fixed driver was available, the only workaround was to disable Memory Integrity:
- Open Windows Security > Device Security > Core isolation details.
- Toggle Memory integrity to Off.
- Restart the PC to apply the change.
Note that this lowers the system's protection against kernel-level exploits, and may be restricted or blocked by IT policy on managed lab PCs. The updated driver above avoids this trade-off and is the recommended fix.
Affected / not affected products
-
Affected: PicoHarp 300, HydraHarp 400, MicroTime 200 (all use the
pqusb64.sysdriver). - Not affected: MultiHarp, PicoHarp 330, HydraHarp 500 — these use a different driver and do not have the Core Isolation conflict.