I use the following powershell script to inventory the installed features with there ID. (MOSS , change 12 to 14 for SharePoint 2010)

 

$results=Get-ChildItem “c:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\FEATURES\” feature.xml –rec
foreach ($File in $results)
{
   [xml]$feat=gc $file.pspath
   $feat.feature | Select ID, Title, Scope
}