From Windows XP Newsgroups....
1. Determine the location of the Msiexec.exe file on your hard disk. To do
this, follow these steps: a.  Click Start, click Run, type %windir%\system32,
and then click OK.

Note This step will open the folder where the Msiexec.exe file is located.
b.  Make a note of the location of the Msiexec.exe file. The location of the
Msiexec.exe file will be a combination of the value in the Address text box
and the Msiexec.exe file name itself.

For example if the Address text box contains a value of C:\Windows\system32,
the location of the Msiexec.exe file will be C:\Windows\system32\Msiexec.exe.
----
OK...I'm trying the following steps and got to the hidden files.   There is I
can find C:\Windows\System32\msiexec; but there is not an entry for
...\msiexec.exe.  Is it included in the ...\msiexec?   Or have I lost this
file?  Is there a way to restore it?

I have also tried to uninstall Office (system came with 2003 and a trial
period, but I have never used...I've been using my Office 2000).  Windows
Installer will not allow me to uninstall either of these programs since
Installer cannot be found.  

I have not dared mess with the registry keys since information shows it is
for the experienced user/professional.   Not me!

Sue