When you use the Computer Migration Wizard in Active Directory Migration Tool version 3.2, the option to specify an include file for computer migration objects does not function correctly. If you select the “Read objects from an include file" option in the wizard, you cannot proceed to the next wizard page.
Read more at http://support.microsoft.com/kb/2327195
As a workaround, you can specify the include file by running ADMT from the command line. For example, to specify an include file for computer migration as part of an intraforest migration, type the following command:
ADMT computer /F:<include file> /IF:YES /SD:"<source_domain>” /TD:"<target_domain>" /TO:"<target_OU>" /RDL:1
/IF:YES – Use this option only when performing a intra-forest migration.
/RDL – Change the restart delay value in minutes based on your requirement.
Other Related Articles:
Active Directory Migration Using ADMT - http://www.sivarajan.com/admt.html
Computer Migration - Things to Consider - http://www.sivarajan.com/cm.html
User Account Migration and Merging Using ADMT - http://www.sivarajan.com/