That gives me the intention of a trial!
As far as I followed the discussion, the 20 is the better start. Correct?
'pe2' develpoment has stopped, so if you find any bugs, you will need to fix them yourself! It was working OK... for me, at least... not a lot of feed back. The WAIK for that one is v.1.0
'pe21' is under development, and if you find any bugs, you can fix them
yourself too! ...
... It has many more features and programs, so would be the better choice. It requires the WAIK for VistaSP1/Server 2008. When I updated to the latest WAIK, the installer said to uninstall the previous version first. I simply renamed the existing 'Program Files\Windows AIK\' folder to 'Windows AIK 1.0' in case I needed the old version again.
I hope I caught you before the big ( > 1GB ) download... if download-capacity is an issue for you - it is for some people.
Burn the download to DVD, and start the DVD's autorun (re-insert the DVD), and select the 'setup' to install the WAIK (preferrably to default 'Program Files'). Requirements like .NET 2 and MSXML will be detected. There is also a HotFix on the DVD for imagex.exe use on some computers (... not sure when it is required?). And if you require a Language other than en-US, copy the 'WinPE_LangPacks\' folder from the DVD to HDD, or leave the DVD in the drive, and browse to it from the pe2/pe21 interface.