There are many Electrum users affected with this phishing exploit until now those Electrum user's who use an old version of Electrum will suffer from this update without asking here or in
electrum.org support.
I think OP doesn't need to reinstall a new fresh OS just uninstall the Electrum and go to C:\Users\admin\AppData\Roaming then find the electrum folder and delete them all after than goto C:\Program Files and find electrum folder again and delete them all.
Or if you want to delete all every trace of electrum wallet you need to use
Iobit Advanced Uninstaller.
So that you can fully uninstall and remove all electrum files and traces including traces on regedit.
Now, you can install the new electrum wallet. Just make sure that you download the electrum directly from the official website here
https://electrum.org/#download