I am having the same problem, except it affects all installs that use the
windows installer. Some give the error 1500 and then the message, others
just give the message. The windows installer message comes up with almost
every new window opened. I cannot install the cleanup utility, I cannot
update programs. I have deleted the Inprogress key from the registry with no
effect. I have used a program called regcure and scanned until it comes up
clean. Still the same thing. I am of the opinion that my windows installer
program is bad but it does not seems to be available for replacement. I have
restored my computer to the earliest dat available, again without any effect.
I believe this all started with an install of Nero Ultimate 7. I have tried
to uninstall this program and office 2003, none of which will work due to the
error 1500. I have too much valuable information to start over and really
would like to find a fix. I assume there is one as the threads on this
subject just seem to stop, although I have yet to find an answer.