Yes, they are the backups for uninstalling a hotfix, however, that is highly recommended against. It won't do any harm to your system by removing them. Check out my blog post about system maintenance here. so what you're saying is that i could (and should) delete all those folders in C:\windows that begin with $NtUninstallKBxxxxxxx? as well as the $hf_mig$ folder? that they serve no purpose? thx. just one question... i had always thought, perhaps erroneously, that the MS windows update site checked those exact folders to see which updates one was lacking... if that is the case, then if i deleted all those folders it would report that i needed to install all those updates again. plz enlighten me about that if you can...