I am currently building a WinPE 4 ISO and I am wondering why the ISO file keeps growing after every commit and iso build. All i am changing is some lines of powershell code, which for sure are not as long as 1 MB.

name: winpe4_v16.iso size: 305'131'520 bytes

name: winpe4_v17.iso size: 306'417'664 bytes

name: winpe4_v18.iso size: 307'703'808 bytes


I have noticed this too. When I'm done with any particular set of updates, I export the image to a new one. The less memory used on a PXE boot, the better.

When you modify an image, DISM stores additional resource files that increase the overall size of the image. Exporting the image will remove unnecessary resource files.


  • Yeah, whenever I build a new WinPE image I just completely regenerate, it keeps them lean, clean, and mean. – MDT Guy Dec 6 '13 at 21:44
  • dism.exe /export-image /sourceimagefile:boot.wim /sourceindex:1 /destinationimagefile:temp\boot.wim /compress:max – Matze Dec 9 '13 at 10:50

Extra technical details, those are not 'additional resource' files but actually orphaned/replaced files that are no longer part of 'any' images inside the .wim.

For example, in this single image install.wim, orphan files end up in the internal 'Files' folder after being deleted from the (1) image. When exporting the (1) image they are skipped. Limitation of the .wim format, no known internal delete mechanism.

7z file manager view inside .wim

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