Internet Explorer 8 ships with a feature to increase reliability by spreading tabs across multiple processes, unfortunately if you want to profile (or debug) a plugin (Silverlight, Flash etc) then you need to know the correct process ID (PID) to profile, as the normal PID will usually be of the iexplore.exe container, as opposed to the tab that you want to target.

To make things easy, you can disable per-tab processes by modifying the following key\value:

HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main\TabProcGrowth

This vale may not exist, so go ahead and create it as a DWORD with a value of 0. To restore normal IE8 operations (I personally run with it constantly disabled and haven’t seen much of an adverse affect, but on lower powered machines or if you’re not constantly profiling) just delete TabProcGrowth.

You can also automate this by adding it to a .reg file or by using the following command line commands (in a batch file etc):

Disable TabProcGrowth

reg add "HKCU\SOFTWARE\Microsoft\Internet Explorer\Main" /v TabProcGrowth /t REG_DWORD /d 0 /f

Back to default

reg delete "HKCU\Software\Microsoft\Internet Explorer\Main" /v TabProcGrowth /f