Open Task Manager > Services or run services.msc:
If you can’t stop a service, open Command Prompt as Admin and run: hikvision error code hcnetsdkdll 23 install
net stop "HikService"
Hikvision software loves to run in the background. If you have the iVMS-4200 client minimized to the system tray, or if the "Storage Server" service is running, the HCNetSDK.dll file is currently in use. Windows will not allow the installer to overwrite the file if it is locked by a running process. Open Task Manager > Services or run services
How to force close background processes: If you can’t stop a service, open Command
Use dumpbin (Visual Studio tool) or Dependencies (open-source):
dumpbin /dependents C:\Program Files (x86)\Hikvision\SDK\hcnetsdk.dll
Look for any missing DLLs (marked "NOT FOUND").