windows - Starting Multiple Internet Explorers in a Batch File

In Windows XP, I am trying to start multiple IE7 with a batch file like this:

@echo on
"c:\windows\explorer.exe"
"c:\windows\explorer.exe"
"c:\Program Files\Internet Explorer\iexplore.exe"
"c:\Program Files\Internet Explorer\iexplore.exe"

The above program starts 2 concurrent copies of Explorer.exe successfully. But it just start 1st copy of IE7 and stops there waiting for it to terminate before proceeding to the next line to start the 2nd copy. And it is until the 2nd IE7 process terminates that the batch file's console window disappears.

How can I start 2 concurrent IE7's and have the batch file console finishes immediately? Just like in UNIX sh we would add an "&" after the executable file name to create a background process.

Actually, what bothers me is why there is a difference in behaviour among starting explorer.exe vs iexplorer.exe?