Content Cleanup Required
From easier (1) to the more difficult (4):
1) Click on System > Administration > Update Manager > Click on Check button > Apply all updates including kernel.
2) Use Synaptic, search for linux-image and select the generic kernel version you want to install (i.e. linux-image-2.6.xx-yy-generic).
4) Run the following Terminal commands to install a new 32-bit Ubuntu kernel from http://kernel.ubuntu.com/~kernel-ppa/mainline/
sudo apt-get update
sudo apt-get install python-bs4
rm -rf medigeek-kmp*
wget --no-check-certificate https://github.com/medigeek/kmp-downloader/tarball/master -O kmpd.tar.gz
tar xzf kmpd.tar.gz
python kmpd.py -d
The script at https://github.com/medigeek/kmp-downloader/ does not seem to allow choosing amd64 (64-bit) architecture. It only allows installing i386 (32-bit) architecture. This seems like a bug to me. Just press <ENTER> instead of a number if you get stuck on a certain question in the python script.
Roll-back and uninstallation
You can roll back by selecting the previous (old) kernel at the boot menu and then uninstall the (new) not working kernel.
With Synaptic you can uninstall previously installed kernel packages.