It’s been a tip season and I am longing to tell you this piece of information for ages!
You can run light weight applications during Windows Vista setup and even things like explorer after the second reboot.
This magic works because Vista’s setup runs in a mini Windows installation called Windows PE-Windows Pre execution Environment. This is a full blown Windows environment that exposes just enough facilities to give you a 32/64-bit GDI based GUI. I tried to take a picture to show you how to do but save/save as in paint didn’t work. Due to COM registration issue in that part of setup, showdocvw.dll was not registered at that point and explorer gave an error (refused to lanuch) and there was no way to save the snap-shot. However, after the second reboot, I was able to run things like cmd.exe, taskmgr.exe, explorer.exe and devmgmt.msc and GOD devmgmt.msc showed devices installing in real time.
The trick to do stuff like this starts with getting a hold of command prompt which can be run by pressing SHIFT+F10 keys. Now, this step is document and recommended only if you ‘really‘ need to have access to a command prompt. I went ahead to tried to run things from that command prompt and most worked. Next you have a choice to run an application of your choice from the command line. Remember that application should not rely on things like COM registration or OLE automation. These things are not initialized properly during that stage of setup.