Pre Windows Vista, you could find the version of Internet Explorer via WMI using the following method:

strComputer = "."
Set objWMIService = GetObject("winmgmts:\\" & strComputer & _
Set colIESettings = objWMIService.ExecQuery _
    ("Select * from MicrosoftIE_Summary")
For Each strIESetting in colIESettings
    Wscript.Echo "Version: " & strIESetting.Version
    Wscript.Echo "Product ID: " & strIESetting.ProductID
    Wscript.Echo "Cipher strength: " & strIESetting.CipherStrength

The MicrosoftIE_Summary object does not exist post Windows XP though (Why Microsoft, why?), so to find your browser versions, you could use the following VB Script, which essentially just checks the file version for you.

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