Trying to get Firefox to open in User Agent "Internet Explorer"

Question

I run an Internet Cafe and have recently installed Ubuntu 10.04 over Micro$oft.
I HAVE to give customers an alternative to Live Messenger.
I have TokBox setup .. but gives problems now & then.
I need to cover all bases or lose customers.
The only viable alternative I have found is '''EBuddy'''.
Now the problem is .. when I log in using Internet Explorer and I connect to a contact - I can see the start video call "button".
Any other browser and the webcam button does not show.
All of the Firefox & Seamonkey User Agent Switchers I have tried work .. but I cannot expect the customer to know that they need to switch User Agent before they can use the webcam.
I need to Launch either Firefox or Seamonkey (preferably Seamonkey - if the fix is to be a permanent one) in Internet Explorer mode.
A permanent "fix" for Firefox was suggested on the Ubuntu Forum ...
1. Open about:config
2. Right-click, choose "New" > "String"
3. Type "general.useragent.override" (no parentheses) into the "New String Value" dialog box that appears and press "Enter." Type or copy and paste the desired new user agent string into the "Enter String Value" box (in this case "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1)" )
When you're done, copy that Firefox profile to all of your computers (the .mozilla folder)
I tried this on Seamonkey .. but it did not have the desired effect = no start video call button.
There is a Proxy Tool add on for Seamonkey which can change the user agent and this works. Same thing for Firefox.
But the user agent is back to default on browser re-start.
In an ideal world I would like to create a Launcher on Ubuntu desktop which would open either Firefox or Seamonkey on the E Buddy sign in page and the User Agent would automatically be set to IE8 or 9.

Answer 1

Try to set the user agent via a user.js file.
*http://kb.mozillazine.org/user.js_file
user_pref("general.useragent.override", "<IE user agent>");