How to Login into Orkut and Gmail with Different IDs
Method 1: Works only on firefox
Make different profiles in firefox and then login into gmail and orkut from different profiles. Here’s the procedure-
Step 1:
Open system properties(by right clicking my computer), choose advanced tab, click to environment variables button. Now in the system variables section, click new. type this information to each textbox.
variable name: moz_no_remote (should be all small letter).
variable value: 1
Step 2:
Open firefox icon’s properties(from desktop and quick launch, simply right click on each and click properties). Add extension -p to command line (like “c:\program files\mozilla firefox\firefox.exe” -p). Press OK.
Now when you’ll open firefox, it’ll ask you to choose the profile. Simply create a couple of profiles. Since each of these profiles are mutually exclusive, you can login with different google accounts in different profiles.
Method 2: Commonsense Approach
Just install more than one browsers and then login with different IDs in different browsers. Simple? 
i can’t add the extension -p to command line in mozilla firefox….
it say “C:\Program Files\Mozilla Firefox\firefox.exe”-p is not a valid path
i have change the system variables..
Amit, this may be because the firefox is installed in some other location. You can read this updated tutorial to learn everything about firefox profiles.