What is the $hf_mig$ directory for in Windows Server 2003?
Solution 1:
Its name means "hotfix migration". It's for tracking versioning information about hotfixes to keep from accidentally breaking or downgrading your system. No, you definitely should not delete it.
Solution 2:
Here's a good explanation of the topic: What is the “$hf_mig$” Folder for And Can I Delete It?