Windows Installer - Maintenance Mode via msiexec or .msi

I just began to test .msi installations on Vista and I know very little. I
can double-click a .msi installation written using InstallShield 10.5 and it
installs ok. But when I double-click it again or run it using msiexec in
order to go into Maintenance Mode I get a security error saying it isn't
allowed as I don't have the correct privileges. Yet, I have Administrator
privileges which allowed me to install it in the first place. I can only get
into Maintenance Mode if I go through the Control Panel. Why can't I get
into Maintenance Mode via msiexec or double-clicking the .msi like I can on
previous operating systems? Is there a security policy I can change?

Also, will I be able to perform minor updates of the product I installed as
I have before when I run the msiexec command with the REINSTALL and
REINSTALLMODE parameters?

 

I'm still testing our legacy installations and our Vista system has been
reloaded and now I can get into Maintenance Mode via msiexec or
double-clicking the .msi. I don't know what changed. Supposedly the Vista
build was the same - Beta 2 build 5384. If anybody knows what might have
caused the previous problematic behavior I'd still like to know.

I still have an issue with performing a minor update using a full .msi.
When I enter the following from the Run command or from a VBScript:

msiexec /i "c:\test.msi" REINSTALL=ALL REINSTALLMODE=vomus /qb

I get the following error:

"The system administrator has set policies to prevent this installation"

In order to successfully install the update I figured out I can do one of
two things:

1) Enable the AllowLockdownBrowse policy (Enable user to browse for source
while elevated).
2) Right-click on the Command Prompt and "Run as Administrator".

Are either of those the methods of accomplishing this task the correct way
of doing it? Is one preferred over the other? Is there some code somebody
can point me to that I can put in a VBScript that will verify/ask the user
for Administrator credentials and then when the script runs msiexec the .msi
will inherit the Administrator credentials and install? Is there another
way? Is there a Vista bug that should have automatically asked me if I was
sure I wanted to perform the update instead of just failing?

Answers to any of my questions will be appreciated.

Thank you,
Scott