the efisys.bin is found in: \efi\microsoft\boot\efisys.bin dude, this post was amazing... it helped me A LOT! so i'm finishing my vista OEM pt-BR under windows xp right now... my custom batch file: CLS @echo off TITLE Criando imagem UDF do Windows Vista ECHO. ECHO Sua imagem está sendo criada. Tenha certeza que oscdimg.exe está presente. ECHO. ECHO Criando sua UDF... oscdimg -h -n –m -u -u1 -u2 -bD:\VistaWork\DVD\efi\microsoft\boot\efisys.bin -lFRMCXFRE_BR_DVD D:\VistaWork\DVD\ D:\FRMCXFRE_BR_DVD.iso ECHO. PAUSE EXIT sorry, the topic is very old, but im SO HAPPY! thank you guys!