Fixing display issues on Intel 82845GL

Unity 2D is designed for old chipsets such as the 845 and 855 intel series.

Your issues are most probably due to buggy old drivers together with Compiz incompatibilities.

Suggest boot into recovery mode - with network support. Then install unity-2D

• How do I install and switch to the Unity 2D desktop?

I have found with my i855 laptop that I need to boot with an extra grub parameter otherwise I get a similar login screwed up display -

can I suggest that you also see if either grub string i915.modeset=0 or i915.modeset=1 works for your PC. Follow my answer here on how to add it to grub - instructions also include how to fix in grub permanently.

As an alternative to Unity-2D, you could try a light-weight distribution such as Lubuntu (or possibly Xubuntu) which should work much better with very old graphics chipsets such as the i8xx chipsets.

The Intel 845 series chips have serious hardware errata. The Windows drivers at the time and the old Linux driver stack didn't exercise the parts of the hardware that don't work, so didn't run into problems.

The new Linux graphics stack (GEM/KMS/DRI2) exercises these hardware features. We disabled the Intel driver on your card because of this. This is why Unity doesn't work for you. See this answer for more details.

The video mode issue would appear to be a different problem. Logs (dmesg and /var/log/Xorg.0.log) are the price of admission for debugging that sort of problem.