Over the weekend, in preparation for an upcoming review of the newest versions of Fusion and VirtualBox, I needed to set up a new Boot Camp partition on my MacBook Pro. Because Windows 7 isn't yet officially supported by Apple, and Vista isn't widely used, I chose to install XP Pro. My XP Pro disc is a Service Pack 2 release, so after booting into Windows, the system found and downloaded a bunch of updates to apply, chief among them Service Pack 3 (SP3).
The update process went smoothly, until the system tried to install SP3. The update process started, then died with this error:
An error occured while copying file osloader.ntd. Cannot copy file to destination directory. Click Retry to retry the operation or click Cancel.At that point, the only solution was to bail on the update, and have Windows back out the changes it had already made. I tried a few times, but always got stuck at the same point. After a fair bit of digging and hair pulling, I found this Apple Support document that describes the problem, its cause, and (most importantly) the solution.
To get around this problem, you need to first back out of the SP3 installer (which involves a series of clicking various No, OK, and Cancel buttons).
Once out of the installer, you need to rename a file buried inside the Windows system files. On your Boot Camp partition, navigate into Windows » System 32 » drivers. Here you'll find a file named AppleMNT (it's a .sys file). Rename it to AppleMNT_keep, then restart Windows.
After the restart, verify that your Mac OS partition no longer shows in the My Computer window, then install SP3. When it's done and you've restarted, rename the AppleMNT_keep file to AppleMNT, and restart again to regain read-only access to your Mac OS partition. I'm glad to report this worked as described, and SP3 is now installed and running on my MacBook Pro.
Mac OS X Hints