Downloaded and installed Digital Editions (as computer had lost previous installation) and downloaded ascm file from my local library (UK). When I opened it on my computer I wasn't asked for my adobe id, as previously, I was asked for a vendor id, which I don't have from my library so I just clicked to register anonymously, or whatever it says. However I want to read this mainly on my android, which I have done before, but now the android says the content is already fulfilled by another user - which is me on my computer. How can I access it on my android as I will never read the whole book on a desktop screen (just opened it to have a quick look) - I only have 3 weeks before I have to return the book.
You can't at this point.
"now the android says the content is already fulfilled by another user - which is me on my computer"
Not you on your computer, but an anonymous user on your computer - which since it is anonymous can't be authorized to anybody else.
Moral of the story is - don't activate anonymously (in the login dialg that said Vendor ID, IIRC the VendorID should be a drop down that lets you select AdobeID)