[KaktoR]

You have two choices:
1. Rename Setup.dll (which DSG creates) to Setup.arc and extract the file into DECOMPRESSOR folder with FreeArc.
2. In DiskSpan_GUI folder, go to "Resources\INSTALLER" and pick the files you need and copy them to DECOMPRESSOR folder.

For the second choice you have to pay attention to some things:
1. If you used precompressors like XTool, you have to create a folder with the same name in DECOMPRESSOR folder like the precompressor you used.
2. ARC_*.ini and CLS_*.ini are required in any case.

In your methods srep+msc and srep+lolz you have to copy the following files:
"Resources\INSTALLER\ARC\*" (all files here)
"Resources\INSTALLER\LOLZ\*" (all files)
"Resources\INSTALLER\MSC\CLS-MSC_TAK.dll"
"Resources\INSTALLER\SREP\CLS-SREP_NEW*.*"

However I recommend to follow the first choice, as it is the simpliest way.