It may be that the publishers have stopped providing those books.
In that case you may be a stuck if you only have the .acsm files.
Try contacting the publishers and see if they can help. Good luck.
Depending what you managed to recover from the crashed system before reformatting,
you may still have the old .epub files around.
If you can find those you should be able to open them without any further downloading.
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As a general comment (too late for you now maybe, but for others that might read this thread, and for you looking forward):
The Adobe DRM system is only for DRM.
It does NOT automatically keep copies of your library somewhere for you to redownload after problems.
You should keep a backup copy of all your books (the .epub files) just in case of such a failure.