Having had a bad experience with 64 bit vista, I have now found out that the same flaw is present in win 7 64 bit.
The problem is that after a restart 1 or more drives will be reset to 'read only', the pain of it is the only way I can remove the 'read only' attribute is by formatting the drive and resetting the permissions. Which is painful due to the time involved, having to copy files to another drive then back again after the format.
click here does not work as its the actual drive that has the 'read only' not the files, plus there are no options to delete or change files only copy.
So until this matter has been cured its back to 32 bit xp for now.
By the way, this only happens with 64 vista and win 7 not the 32 bit versions.