Solved Error Message While Installing BitDefender On XP

After removing AVG, due to some recent gliches, where the UI was showing without any content, just a rectangular blank space every so often, which when clicked on, disappeared to the task bar (fortunately at least I could get it out of the way), I decided to install Bitdefender, and after downloading the install file, unplugged my computer from the internet, as I now was operating without protection, at least temporarily, until I installed BD.
Then, when I moved the install file to the desktop, and double-clicked it, I got an error window entitled “installer.exe – Entry Point Not Found”, with the following message: “The procedure entry point GetPhysicallyInstalledSystemMemory could not be located in the dynamic link library KERNEL32.dll.”
What should be my next step, short of replacing this computer with another, newer one? (still an option). I don’t want to re-attach it to the internet without some kind of protection.