PC or Mac?
If it's a PC those settings might be in the registry, which is best edited by someone who knows their way around there.
For a Mac, a preferences file should be under the "Library...Preferences" folders. Beware though, I deleted my preferences file for ScanFast, which was a solution their website recommended for a problem I had, and it has never worked correctly since. Though you have little to lose.
You could try uninstalling, then deleting any references in the Registry or preferences, then re-installing. But if that doesn't resolve it, it's probably a hardware fault.