Maybe the questions are too old and asked somewhere else....

1.What's the $OEM$ directory structure in Vista(please provide a complete list of directories possible) and how to get some files copied on my Desktop during Unattended Install?

2.How to import a registry tweak silently- does vlite provide such facilities?

3.Do i need to modify 'autounattended.xml' file made by vLite to apply my reg tweaks?

extracted iso x:\Vista DVD\sources\$OEMS$

-$$ = %windir% = x:\Windows (x is your boot drive with windows instalation)
-$Docs\All users\Desktop = there you can put your files, after install it will be on desktop
-$Docs\All users\Start Menu\Programs\Startup = can put shortcut pointing on command file which is run after first load of desktop (import tweaks)
-$Progs = equivalent to Program Files

Hope this little help :-)