SystemWorks (or rather each of the components) is terribly bloated these days. Norton Antivirus used to be small and fast, now it's been "XPified" and simply is slow. My suggestion is to uninstall ALL of it, and install just NAV (it's a file with a .msi extension in the NAV folder on the CD, which uses the Microsoft Installer rather than having the executable integrated in the file).
There's really nothing of value in Norton Systemworks anymore. SpeedDisk and Disk Doctor both use the built-in APIs for WindowsXP to do disk defragmenting and scanning, so there's no difference between using those or the standard XP apps to do it. Protected Recycle Bin is just annoying. Most of the other tools in Norton Utilities are either things not many people really need that just sit in the background hogging memory, or they're freely available from other sources. CleanSweep is pretty useless really unless you're installing and uninstalling things daily. "Crash protection" apps have always done more to slow down a system and CAUSE crashes than they've ever prevented. Things like the "web cleanup" and "connection keep alive" have been available in freeware for years. GoBack can be installed separately and may be part of your slowdown; I'm not sure how much active monitoring it does.
At the very least, you should be able to stop some of the tools from being loaded on startup, even if they're installed. Right click the icon(s) in the system tray and either exit them or go to their properties and see if there's an option to not load on startup. If nothing else, you can use msconfig to stop them being loaded manually. Norton Antivirus is the only thing that needs to be running in the background (Protected Recycle Bin doesn't have an icon in the system tray).