Error on Installing under Windows Vista leads to inability to uninstall

Hello. I have tried to install the following on my Windows Vista Home Premium System: php-5.2.3-win32-installer.msi It has the following md5 sum, taken locally on my system: 4d042f649d9c264477e1b421c64c6435 Installation seemed to go as expected. However, near the end of the installation process, I received a dialog window titled "PHP 5.2.3 Setup" with only an "OK" button and the following message: "The installer has encountered an unexpected error installing this package. This may indicate a problem with this package. The error code is 2738." I pressed "OK", my only option, and then got to the page on the setup wizard with the "Finish" button. I hit the "Finish" button, was met with a dialog window with just an OK button with the message: "Fatal error during installation". It seems that PHP was put on my system, and the path was set up correctly. Some simple tests indicate it is working, however, since I am a careful sort, I thought I would try to uninstall and start over. The trouble is that I can't. I can use the "Repair" option from ControlPanel->ProgramsAndFeatures->PHP, and it seems to "repair" without comment, but if I try to uninstall the software, or "Change" it in any way, I get the same two dialog boxes shown above, and the software does NOT uninstall. This makes me uneasy. I would appreciate help with any of the following (roughly in my priority order): 1. How can I uninstall this and remove it from my system? 2. What is error code 2738 and what does it mean? 3. What steps might I take subsequently to install without incurring this error? Thanks in advance for any assistance. -Stephan G