[dba-SQLServer] Read-only databases?

Now I've gone and buggered things up nicely. I was running out of space on
drive c:\ so I decided to move all my SQL databases to drive e:\. I've done
that many times without incident:

1. Detach the database(s) in question.
2. Move it to the new location.
3. Re-attach the database.

However, this time it didn't work. Several databases were attached, all
right, but are marked read-only. And two databases could not be attached.
The message I got said that the files are read-only and the fix is to change
their attributes.

How do I change the first group of databases so they are not read-only?
I checked the attributes of the second group of files and they are not
marked read-only.

What is the problem here? Any suggestions?

Thanks,
Arthur