If you are still using that PC, you can uninstall these software, and unclog your computer.
Go to Start
--> Control Panel
--> Add/Remove Programs
-->Find the Norton program and any other unwanted software that came with the box.
--> Click Change
--> Remove All.
Then to delete the registry file, install CCleaner
Go to the "registry" button, and "scan for issues".
I must warn you, look at the file path in the "data" column that CCleaner shows after its scan.
Any registry file with the path from Microsoft Office (ex=> C:\Program Files\Microsoft Office11\)
UNCHECK these files, and click the "Fix selected issues button"
This will delete any remnant registry files from old installed programs and software, that lags the system.
If you don't you'll find that the Microsoft office programs such as word or excel to be corrupted.
Uncheck any other files that you are familiar with, and you use often.
Unclogging the registry will speed up your PC.
Most importantly, do this at your own discretion, playing with the registry is a risky business (Making a backup or a restore point is a good idea before doing this).