On a netbook I tried to uninstall all of its bloatware, which was like 5 GB or so. After some uninstalled programs, it began to uninstall the rest very slowly and at a certain point all uninstalls would freeze to death forcing me to kill the task and to reboot the PC if I wanted to uninstall something else as the uninstaller said it was already running when it wasn't.

I've searched all around to solve the problem but I have been unable to find a solution. Do I have to reinstall windows installer or what?

uninstaller said it was already running when it wasn't.

have you restarted the netbook

Bloatware. List it. Some companies, like HP, install their own versions of drivers, services. You remove it and discover it was valid, necessary too, even though perhaps bloated with unwanted options and company branding. You possibly removed something that the chipset required.
For some it pays to buy a naked sys and a copy of the M$ bloatware [Windows].

I've found a strange message saying that an installation is on halt, even if I reboot the computer. It then prompts me to undo the changes that were made, but freezes no matter what I do.