Hi Rhys. I'm Greg, 10 years awarded Windows MVP, specializing in Installation, Performance, Troubleshooting and Activation, here to help you.
Did you use some 3rd party download location or the official Adobe website?
Why is McAfee on your PC? Are you not aware that every expert warns against using it? Usually when it's mentioned we've found the problem. But not knowing that and using McAfee often means many other ruinous apps like optimizer suites and registry cleaners are used which are death to Windows.
So let's unplug the external and start with cleaning up Windows, then we can troubleshoot the external, disinfect, clean and reformat it as necessary.
- To check most thoroughly for infection and any resulting System damage, Download, install and run a full scan with the most powerful on-demand free scanner Malwarebytes:
https://www.malwarebytes.com/mwb-download/ Make sure to only choose the Free version.
In the Malwarebytes Settings (gear icon) > Security tab set it to include scanning for Rootkits.
If necessary run it in Safe Mode with Networking (to have internet), or Safe Mode accessed by one of these methods: https://www.digitalcitizen.life/4-ways-boot-saf.... These require a password and not PIN to access.
Clean up anything found, restart PC and then run again until it comes up clean.
Then download, install and run a full scan with AdwCleaner:
http://www.bleepingcomputer.com/download/adwcle...
Remove whatever it finds.
Check for anything found but is still left over in Settings > Apps > Apps & Features, and C:\Program Files and C:\Program Files(86) to uninstall or delete them. I can guide you how to do this if there are problems.
Also in each of your browser's Extensions, Home Page settings, Search service or Add-On's as shown here: https://www.computerhope.com/issues/ch001411.htm
to disable anything you didn't add yourself and are sure you need. Ask back if in doubt.
Then check for damaged System files by running System File Checker and DISM from Step 10 in this checklist:
https://answers.microsoft.com/en-us/windows/for...
- Plug back in the external. Is it showing in File explorer now? If not go into Disk Management, scroll down to find the drive, right click to add a Drive letter.
If it's still not showing up open Device Manager, under Disk Drives see if the external shows up there (usually by model number) and if so from Update driver tab try Update Driver > Automatically. If not then try Update Driver > Browse > Let Me Pick to try all previous drivers. If that fails then try Uninstall, restart PC to reinstall drive.
If the drive is detected run the same scans above. Add a full Disk Check: https://www.groovypost.com/howto/check-hard-dri...
I'll have other steps depending upon what you report back.
If you want to keep Malwarebytes as an on-demand scanner then you can turn off its Real Time trial version using the slider buttons on it's front panel. I recommend it as the #1 tool for your toolbox. For best WIndows performance, use built-in Defender which gives adequate real-time protection.
Feel free to ask back any questions. Report back results for more steps if necessary.
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Standard Disclaimer: There are links to non-Microsoft websites. The pages appear to be providing accurate, safe information. Watch out for ads on the sites that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the sites before you decide to download and install it.