Norton, McAfee, and other subscription based antivirus programs are known to be real resource hogs and bloatware.
Why not use a program or programs that are not only free, but less demanding on your system?
Why not just use free antivirus software that is free all the time? Avast and AVG come to mind. No sense in paying for something that is free and works really well.
Malwarebytes and SpyBot Search & Destroy are free antimalware and antispyware programs. They remove trojan horses, hijacker, malware, spyware, etc.
There are plenty of free antivirus and antispyware/antimaleware programs to choose from. Research (like on CNET.com and other non-biased techie sites) and find the one(s) that best fit your needs.
No subscription fees! Save your money.