The file appears to be a legitimate part of Move Media Player, a media player plugin for internet browsers from Move Networks Inc. However, in this post by another forum member the name of the file on her computer is npmnqmp.dll instead of npmnqmp071301000019.dll
Location of the file on my computer -
C:\Documents and Settings\Owner\Application Data\Mozilla\Firefox\Profiles\by21o03n.default\extensions\email@example.com\platform\WINNT_x86-msvc\plugins\npmnqmp071301000019.dll
operating system: Windows XP Home Edition SP3
browser: FireFox 3.6.13.
firewall: Zone Alarm free
antivirus: Avast Free
Yesterday I ran free versions of Malwarebytes and SuperAntiSpyware and neither found anything. Avast scans once a day and also did not find anything.
I ran Trend Micro today (as step 2 of "4 Simple Steps for removing Spyware, Hijackers, Viruses, and other Malware") because last night I belatedly realized a test I was taking online must have used a key-logger to score my responses - answers had to be typed, not copy-pasted, to be recognized as correct.
Thank you for your time and assistance!