Prevent OS X from seeing a disk previously used for Time Machine as a TM disk I have a slightly flaky old disk which was once used with Time Machine on an old Mac. Since Time Machine is no longer part of my workflow, I'd like to just access this disk like any other HDD. Currently, when I try to delete files I receive the message "The operation can’t be completed because backup items can’t be modified."

Edit: I tried using tmutil associatedisk, but I don't see any old versions when I "Enter Time Machine".
There is a command named bypass that should allow you do remove Time Machine related files. This command should precede the rm command.

The path to the bypass command is given below.

/System/Library/Extensions/TMSafetyNet.kext/Contents/Helpers/bypass


An example is given below.

/System/Library/Extensions/TMSafetyNet.kext/Contents/Helpers/bypass rm -f /path/to/file/name


There also a service written by a third party that allows you do execute the bypass/rm commands from the Finder application. If interested, I could provide a link.