You're most likely running Win8.1 but you may wish to make sure here.
You must address any potential infection issues before considering to upgrade to Windows 10 (if you're planning to do so :).
Now, is it this what you're seeing?
Error code 0x80004004 means 'Operation aborted', which might be due to one or several reasons, including but not limited to inter-connection problems, malware blocking, conflicting security software, other unknown issues.
Most likely malware related since you recently experienced some browser hijacking issues. What have you tried already to solve this? The removal guide suggested above by Bruce may be of assistance.
If Microsoft Antimalware software (WD and MSS) gives you a clean bill, you may wish to go for a second opinion check using other on-demand scanners such as MBAM (Free version only! <= Avoid the 14-day trial of the Premium version which is offered during the install process) and the ESET Online Scanner, to make sure your PC is malware-free. A good anti-adware tool such as AdwCleaner may also be a good idea to ensure there is no Adware or PUP that might have been installed there with or without your knowledge or consent.
If any threats are detected by any of these tools, please do jot down their detection name(s), location, and actions taken.
If the WD's update error persist, try the following diagnostic/troubleshooting steps to check:
- Make sure there is no other real-time protection program installed (or remnants of it) on the OS, and also check out there are no other possible issues that may affect WD on Win8.1. See: Windows Defender on Windows 8.1 - Introduction and Frequently Asked Questions.
- Run a SFC scan to repair missing or corrupted system files (if any). Also see: Problems starting Windows Defender in Windows 8/8.1
- Go to Windows Update and manually check for updates. Download and install any Defender signature update that is offered.
You may also try to manually download the (large file with engine and full definitions) latest definitions directly from the MMPC portal here. Please note that this is a 'silent install' - nothing will appear to happen when you double-click the downloaded file, but it shall be installed behind the scenes.
Also see: Troubleshooting General Errors while Updating.
- If the issue persist, you may wish to consider a refresh (or other options) of the OS.
Please return to this thread to tell us how it goes.