Norton's end user products are junk...Sorry but working in the IT field for over 25years ive seen more infected PCs using Norton than anything else. Its one of the worst for actually deleting the threats even if it finds them.
Their corporate products are much better. Its called Endpoint and sold under the Symantec name instead.
https://www.symantec.com/products/endpoint-protection
Get a free version of Malwarebytes and/or SuperAntiSpyware. Install them in freeware mode. NOT THE FREE TRIAL. Run one of them and see what they find. The freeware versions are just a scanner/remover. It wont run all the time. You might be surprised.
https://www.malwarebytes.com/mwb-download/
http://www.superantispyware.com/download.html
Ive had very good results with Emsisoft's Emergency Kit also. This one can even be used from a thumbdrive. You extract it into a folder and run it from there. It installs nothing into Windows but updates are slow.
https://www.emsisoft.com/en/software/eek/
https://www.emsisoft.com/en/software/eek/download/