A lot of problems and solutions are available on the net for the error message "Source server does not meet minimum requirements for migration" while performing a migration from Small Business Server 2003 to SBS 2008. This error pops up just before the Migration Wizard starts and after reading the answer file SBSAnswerFile.xml.
Since me and one of my colleagues just spend a Friday night searching, an extra post/article could be helpful for others.
Our issue was caused by using two versions of the SBS 2008 DVDs. One with SP integrated, and one without. In the new DVD, the SourceTool has been updated.
An important change is that the new tool has an installation package (SourceTool.MSI) while the existing one is a standalone executable (SourceTool.exe). This MSI package needs to be installed on the source domain controller. The new tool must be used with the new media. The new tool will work with older media, but not the other way around.