Here's the fix for SP3 keys being regected during unattened instal

[mistr_e]

It turn's out if you slipstream your copy of SP3 into your SP2 in VISTA your unattended install will stop at the product key screen. If you slipstream SP3 while in XP the issue goes away.

So basically if you plan on slipstreaming SP3 do it in XP, I've tried it and it works.

Check Shashank's (MS Employee) post #355

http://forums.microsoft.com/technet/showpo...=0&pageid=3

[MrCobra]

It's also the same if you slipstream it in XP64.