Ed Felten has a great look at Sony's "fix" for the malicious, crash-inducing rootkits they forced their customers to install in order to listen to the CDs they bought:
The update is more than 3.5 megabytes in size, and it appears to contain new versions of almost all the files included in the initial installation of the entire DRM system, as well as creating some new files. In short, they're not just taking away the rootkit-like function — they're almost certainly adding things to the system as well. And once again, they're not disclosing what they're doing.
No doubt they'll ask us to just trust them. I wouldn't. The companies still assert — falsely — that the original rootkit-like software "does not compromise security" and "[t]here should be no concern" about it. So I wouldn't put much faith in any claim that the new update is harmless. And the companies claim to have developed "new ways of cloaking files on a hard drive". So I wouldn't derive much comfort from carefully worded assertions that they have removed "the … component .. that has been discussed".