Please try this FAQ: How do I uninstall Piwik?

Hi,
Sounds like the answer "Hey try 'format c:'" from my early days in school ;-( it solves to clean up the mess, but the root cause is not found.

After investigating a little bit more time than you (worksforme label), I figured out that your installation script tries to set a user to the 'tmp' folder - this does not work and I get the message to execute some "cacl" commands to set permissions on the 'tmp' and its subdirs. But looking at the directory permission all existing default permissions (e.g. group IIS_IUSRS) have been removed and some IUSR with (I think) corrupt settings has been set.

For me the problem could be solved by just uploading the data and NOT starting the installation. Instead I directly added the IUSR to the 'tmp' dir with permissions and then created the subfolders manually. Then I was able to start the installation and finish it without a problem.

So I think you should check the process of adding IUSR permission to the the 'tmp' (and maybe more) folders.
I'm running W2k8 R2 with latest updates, it's a German installation.

Thanks for more notes. I wrote works for me because it is well known issue: the web server user creates directories and files, and when you try to delete them it doesn't work because they're owned by the webserver user/group. That's why we created this "uninstall FAQ and script".

That said there is maybe a bug and so maybe it is not a wontfix.

Unfortunately none of the core team developers use windows anymore. Though we want to make Piwik work well on windows (and it does at least for some IIS setups since we are in contact with Microsoft every month via webgallery).

--> if you have more information or you manage to find a bug in Piwik code itself we will happily solve it, but we cannot directly answer your question as we are not windows users or experts. Let us know if you have more info!