Using the tool and steps below, you may disable UAC prompt for the specific application. This does not disable the User Acount Control feature for the whole computer.

1. Download and install the Application Compatibility Toolkit from this link:Microsoft Application Compatibility Toolkit 5.0
http://www.microsoft.com/downloads/details.aspx?FamilyId=24DA89E9-B581-47B0-B45E-492DD6DA2971&displaylang=en (http://www.microsoft.com/downloads/details.aspx?FamilyId=24DA89E9-B581-47B0-B45E-492DD6DA2971&displaylang=en)

2. In the Start menu, locate the new folder. Find the shortcut icon for Compatibility Administrator. Right click it and clik Run as administrator.

3. In the left hand pane, right-click on the database under Custom Databases and select Create New, and select Application Fix.

4. Enter the name and other details of the application you want to alter behavior on and then browse to it to select it. Click Next.

5. Click Next until you are in the Compatibility Fixes screen. 6. On the Compatibility Fixes screen, find the item RunAsInvoker, and check it.7. Click Next and then Finish.8. Select File and Save As. Save the file as a filename.SDB type file in a directory you will easily find it.9. Copy the <filename>.sdb file to the Vista computer you want to alter the elevation prompt behavior on.

10. Click Start>All Programs>Accessories. Right click Command Prompt and click Run as administrator.

11. Run the command below:

sdbinst <path>\<filename>.sdb

For example, if you saved the .SDB file as abc.sdb in the c:\Windows folder, the command should be like this:

sdbinst  c:\windows\abc.sdb

It should prompt: Installation of <name> complete.

Now do this for each program that annoys the heck out of you with UAC and you should be good to go. This really helps if you share your computer with other users since UAC cannot be disabled on a per-user basis. You get to keep your kids safe (read, “protect them from destroying your computer”) and you get to keep your sanity!

Now how do you disable UAC? 

1. Click on Start -> Control Panel -> User Accounts and Family Safety -> User Accounts -> Turn User Account Control On or Off.
2. Uncheck the box next to “Use User Account Control (UAC) to help protect your computer”
3. Click on “OK”. 
4. It will say you need to reboot, and it isn’t kidding so go ahead and reboot.
5. Once you’ve rebooted into Vista, install Windows Messenger 5.1 and then follow the same instructions above, this time placing the check in the box, to re-enable UAC.

Be careful though, Windows Messenger 5.1 doesn’t like to work very well when a scrollbar appears in a chat window.  This is somehow tied to the “don’t give out your credit card information” message.  More on that later if I can find an easy answer to how to fix it.