Ok, I am going to guess that you probably have quite a bit of junk programs that were not detected by Norton.
Go to the link below and download the IO Bit Uninstaller program.
Install it and open it up.
It will present you a list of software that is install on the computer.
Go through the list and click on the white UNINSTALL button for each one that you don't want or recognize.
Once you go through the list... then click on the circular green/black button at the bottom of the program window.
When that is finished. Go ahead and reboot it. Does it look like it's faster?
I highly recommend uninstalling ALL of Norton related programs. You can use the IO Bit Uninstaller to do that.
Then, download Microsoft Security Essentials at:
I have Malwarebytes Anti-Malware along with MS Security Essentials and I am very well protected and neither program slows down my computer.