what is "removing backup files" installation step

Question

In many windows installers the last step is called "removing backup files".

I understand that to provide transactional integrity of the install process some "backup files" could've been created and have to be cleaned up.

What I do not understand is why on many occasions this step takes considerably longer than the rest of the installation.

Any idea why?

Answer 1

Usually installers create a backup of the current files they are overriding encase the installer fails midway through (or someone cancels) so that they can do a roll back. As far as why it takes considerably longer, it really depends on your computer configuration.