The DMCA, as I understand it, prevents you from modifying content or an application in order to circumvent copyright protection schemes. It also protects programs, applications, etc. from piracy or unauthorized distribution. I don't know what files you are refering to specifically, so I can't be more specific than that.
Copyright laws are entirely different. They protect written and musical works. Coding is considered a written work, and so they fall under both standard copyrighting and the DMCA. And in the US it can also fall under patented technology. The Stanford Libraries has an excellent site dedicated to copyright laws and fair use laws, including the DMCA:
http://fairuse.stanford.edu/
Anyway, your custom ROMs should be okay, as long as you are not altering the code or circumventing copyright protection schemes. Of which, extracting an unsecure compressed file shouldn't be a problem. Neither should making your own installer, as long as the file creator does not object to you hosting the files yourself (in this case you are not altering, but making available).
If you have copied written manuals or instructions from elsewhere, then you are in trouble. Even if you do not file for a copyright license or put a copyright notice on the document, anything a person writes is copyrighted in it's final form, as long as it's an original work and not part of "public domain." Fair use laws allow you to use excerpts from said written works, but not the entire thing, or most of it slightly changed to make it look like your own.
Anyway, it's all very complex. Technically you are not compelled to take anything down unless the copyright holder contacts you directly. Tell your ISP that if they receive notices in the future to tell the sender to contact you directly with the cease and desist order. If you refuse to comply then the copyright holder can get a court order to force your ISP/host to shut your site down. But beyond a court order the ISP/host has no right to do anything to you. Even if it's in the contract, because unless the copyright holder can prove infringement FIRST you can sue your ISP/host for infringing upon your copyrighted work (i.e. your web site) and breach of contract (innocent until proven guilty). By getting your ISP/host to tell people to forward cease and desists directly to you, you can deal with the issue directly and avoid the middle man and court costs on all sides.
Just some friendly advice.
Jammrock