as some of you already know I am working on replacement for ImageX that can be freely distributed (in difference to ImageX which can be legally only obtained as part of the WAIK).

First I made good progress in understanding the WIM file format but now I am confronted with some problems regarding the used compression algorithms:

1. The compression algorithm used for fast compression is currently unknown. I documented all the details I know about it in WimTool Wiki.

Now I want to find out which algorithm is really used. My algorithm comparison method is rather simple but usually effective:

- compress LGPL.txt using a compression tool containing the algorithm to be tested

- open the output file on a hex editor

- search if there is a large binary block that is identical to the compressed file of the WIM file (the compressed LGPL.txt in test_fast.wim starts at offset 0xD0)

A large number of compression tools provided by Microsoft has to be tested and that is the part I am hoping to get some support by all of you here on boot-land. All you need can be found in this attachment:

**wimtest.zip**

**39.36KB**980 downloads.

Please perform the test outlined above and post the results. That would really help me knowing what algorithm it is respectively not is.

In the meanwhile I want to focus myself on finding a library that implements compression/decompression for the MS-LZX compression algorithm (used for compression level maximum).

I am counting on your help,

booty#1