I used succesfully diskpart (on my Windows 7).

In "Command prompt" (Start -> Run -> cmd) type "diskpart" and press enter.
(I wrote "cmd" and then on right click menu I clicked on "Run as administrator").

In diskpart utility (in the same dos window) you have to type "list volume".
You can see your disk (I see all my 4 partitions on the disk that give me the problem) with a progressive number index.
Type "select volume #" and press enter, "#" is the number corresponding to your disk/partition.
Wait the response.
Then type "attributes disk clear readonly" and wait (I wait 2/3 minutes) for the result.

It says that operation was completed, and I can write on my partitions (and run checking/scanning on it).

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