Quoting this from several websites...
nopdb.exe - Here is the scoop on Norton Speeddisk as it pertains to computer network security. The big question: what is nopdb.exe and is it spyware, a trojan and if so, how do I get rid of Norton Speeddisk?
The nopdb.exe process is used by Norton Speeddisk. By default this process is started automatically when your computer boots up. It can be quite resource intensive, so it is recommended to change the settings of the speeddisk component in Norton Utilities/Systemworks to be started manually. nopdb.exe is an application that does NOT appear to be a security risk. The Spy Bot database currently registers nopdb.exe to Symantec. This is part of Norton Systemworks/Utilities. The Spy Bot database is updated often, but inaccuracies may still exist, often caused by viruses named after valid files such as Norton Speeddisk. Always verify your results just to play it safe.
Since it can take up to 80% of computer resources, it is suggested that you disable this. Here's how:
Open Speed disk and go to View > Schedule Options and uncheck Enable Schedule. Also go to Control Panel, Administrative Tools, Settings, and scroll down to Speed Disk. Right click on it and select Manual then Stop and Apply.