First I would disconnect the PC-Power supply because it can damage the Computer and I would replace with another old PC-Power supply that is completely sure it works, not a new one. Otherwise I would try to test Volts at the PC-Power supply. Second I would perform a memory test, it seems that you have to leave it a whole night, I am not sure. Third I would disconnect everything from the motherboard, except the processor and the memory, if necessary I would replace by old hardware that is correctly working. I would neither use network nor DVD-ROM, and I would test if system is still freezing. I would probably try to test during half an hour the hard-disk
If there is not a hardware issue the I would use the gnome-system-monitor to test: Time of CPU & writable memory of the most time-loaded processes to see if this information matches what I am really running on the PC. I would probably try to disable as much as starting processes that I could. I would inspect drivers versions, I would try to reinstall them, I would disable any kind of tools that can be loaded for modem or printers. Probably I would try to re-install Ubuntu in a separate partition with a text-installation, or I would load in a safe mode to test, I would also load a tty console without X-Window to test, from the recovery boot.
Finally I would ask about how to define the run levels at sysv-rc-conf, which seems to be a good tool to configure services.
AMD proccessors are not as quicker as expected, they are much hottest than expected, except a very few of them, which follow the standard architecture as the classical Phenom II x4 or Athlon II x 4. Your processor is a very modern one which is really not enough tested, and which is supposed to need a later implementation by software. Your proccessor has got 6 cores but each two pair of cores share the floating point unit and all the 6 cores share the same L3 cache.
All this info is very confusing for everybody what you can do is to test from Windows OS with http://www.cpubenchmark.net/ This is the best site to test hardware, specially you may compare with itself from other computers also than with Intel i5 2500k, for example. You must download a windows program to test your computer.
You can also test with inxi -v 1 if your NVIDIA Driver Version is the same that is shown at /usr/bin/nvidia-settings, that you should have installed. You should try to use the nvidia driver from nvidia web site, for example for a GeForce GTX 550 the driver is called NVIDIA-Linux-x86_64-295.59.run.
I normally build my computers from components, I do not buy a whole computer. You may ask your dealer to open the PC case and just see if the LM317 chipset (or similar voltage regulator at the power supply), seems a little bit burned. If so it should have its thermal silicone (between this chipset and its cooler) brown.
I should boot with the recovery mode, load to the Network, back again recover the broken packages, delete whatever has been installed and its not necessary,
How can I install Linux Kernel 3.0 in 11.04?
v3.0-oneiric mainline tree.
To try a newer kernel download the following .deb files from the [v3.0-oneiric mainline tree].
headers_i386.deb or headers.amd64.deb depending if you are using 32bit or 64bit
image_i386.deb or image_amd64.deb depending if you are using 32bit or 64bit
sudo dpkg -i *.deb
srs@ubuntu:~$ sudo apt-get install boot-repair
I could not believe that you where in an irrecoverable trouble, as far as I am just beginning in this forum and I see you have got a lot of reputation.
I have tried to understand Linux several years ago, and I could not. I was using an old computer for it. I did not know that Ubuntu at my old computer use to crash because the memory was damaged.
One day I decided to build a new one with a Intel i5 2500k and medium-cost components and cards. I installed 5 distros, during the last 3 months Debian 6 has crashed once while running sensors-detect.