Cannot install Flash Player for Firefox

Question

I am running Windows XP HE with SP4.  IE and the latest version of Firefox are installed.
In both IE and Firefox, on attempting to install Flash Player with the standard link, I get an error message in a small window opens, title "getPlus+(R): Error," text "Unable to load a GUI," "OK" box.  I got around this by locating a standalone installation for IE, which downloaded an installation file to my computer.  However, this does not work in Firefox, even when obtaining access to that link from Firefox.  The file executes, but Flash Player still shows as not installed in Firefox.
I cannot find any separate standalone installer for Flash Player for Firefox.
This error message appears to be generated by the Adobe Installer, a getPlus product.  My thought was to uninstall the Adobe Installer, and try to start over.  However, the Adobe Installer shows up in the list of installed programs reached through Control Panel, BUT clicking the button to uninstall the program does nothing.  The program remains listed.  I cannot find a location for the Adobe Installer program on my disk drive.

Answer 1

As I said in my first message, Adobe DLM appears in the "Add/Remove Programs" dialogue box, but clicking the Remove button doesn't do anything.  The screen flickers for a couple of seconds, and Adobe DLM remains listed as an installed program.  There is no installed program listed under the description getPlus or NOS.
I found useful information at http://www.findmysoft.com/news/Patch-to-Fix-Critical-Adobe-Download-Manager-Vulnerability- Released/ .  Not to put too fine a point on it, information at various locations shows that the DLM has been a troublesome program.
IE did not list Adobe DLM, getPlus, or NOS as an addon.  Firefox listed "getPlusPlus for Adobe 16263" as a plugin. There was not other extension or plugin listed under Adobe DLM, getPlus, or NOS.
Based on the information at the link cited above, I tried the following. First, in Firefox, I disabled the getPlusPlus for Adobe 16263 plugin.  Removing it was not an option.  First, using services.msc, I disabled the getPlus Helper service.  Removing it was not an option.  Third, I deleted the directory c:\Program Files\NOS and its subtree.  I did not find anything relevant in the Application Data directories.
I then went to the link on the Adobe Web site to install Flash Player.  (I know, it's already installed, but I wanted to see if the DLM would now function.)  This time, the first thing that happened upon clicking the link to install it was that the site completed a new installation of DLM.  However, on proceeding to the installation of Flash Player itself, I got the same error message noted above, "A GUI could not be loaded."  So nothing changed.  Opening services.msc again, I noted that the getPlus Helper service had been reinstalled, and was no longer disabled.  The c:\Program Files\NOS directory had been recreated.  I tried manually starting the getPlus Helper service, and trying the installation again through the Adobe Web site.  Same result, no help.  And note that DLM is not being cleaned up automatically as part of this process, as is supposed to happen.
I'm thinking that a previous installation of DLM left behind some corrupted relic that is preventing it from running properly.  Very likely an incorrect registry entry.  But good luck finding that one without help.
NOS Micro has a link to "Contact Our Support Team" at http://www.nosltd.com/index.php/support .  Maybe as a last resort see if they would respond?  Note that I can't locate a way to get support from Adobe except by paying $39.95 per incident for telephone support.
Thanks!