The reason I mentioned a restore is that it does restore the system and rolls back changes to it, even malicious ones. It is also reversible. It does cost time but should fix the problem. But by all means try all the simple fixes first. If you have a large drive there will be quite a few saved for you to go back too. A good precaution in the future is to set a restore point prior to allowing an update.
A Wi FI connection is the Modem software as far as I know not the system, at least my Wi Fi setup is. I feel for you. It can be very frustrating
Here is a forum advice. Apparently antivirus programs can do it Known Win7 problem
If using a system restore point fails to fix it, try running the command sfc /scannow to repair all system files. Or try to do the following:
Tools>options>advanced>security>custom level and under miscellaneous see that "Drag and drop or copy and paste" is checked enable.
Use the internet many suggestions out there. Ask the question you are not alone
The Guy from OZ