BDD 2007 ZTI by default will break on less than 512 MB RAM

The error you get in the ZTIValidate.log is ERROR - 255MB of memory is insufficient.  At least 448MB of memory is required. However, the fix is easy:

1. Make sure you reduce the WinPE size per step 4 in the below article:

Adding a Windows PE 2005 image to WDS (boot-in RAM) 
http://www.deployvista.com/Blog/tabid/70/EntryID/20/Default.aspx

2. Configure customsettings.ini with the ImageMemory value

[Settings]
Priority=Default
Properties=ImageMemory

[Default]
ImageMemory=256