I was attempting to install Ubuntu 12.04 LTS to an albeit antiquated Dell Dimension 4700, but it was to revive an old computer sitting in storage to make it usable for my 7 year old daughter.

I tried installing Ubuntu 12.04 LTS with no success, I tried installing Ubuntu 10.04 along with about 7 other OS's as well, all without success.  I was able to install a Debian based OS called "MineOS Turnkey", which was made specifically to run a Minecraft (game) Server.  That OS installed, and actually worked great for about 3 weeks, then I received an error, rebooted, and the system worked great for a few days, rebooted, system worked great for two days, rebooted, system worked great for a day, rebooted, worked for a few hours, etc...

Prior to me attempting to revive this desktop, I purchased 4 GB of new memory, and installed it to the system, and with the new 4GB of memory, the only thing that would install was the MineOS Turnkey, everything else failed, or just froze during install.  Someone suggested that maybe it was a memory problem, or a HDD problem, so I checked the hard drive, and it was functioning properly.  I pulled 3 of the 4 GB of new memory out of the machine, restarted the machine, and Ubuntu 12.04 LTS loaded like a champ with absolutely no problems.  I shut down the system, added another GB of RAM, and restarted the computer, no problems, shutdown, reinstalled the third GB of memory, and upon reboot, got nothing.  Removed the third GB of RAM, and rebooted the computer, no problem.  So I shutdown, swapped what was the third GB of RAM with what would have been the 4th GB of RAM, and rebooted, no problems.  Shutdown, reinstalled what would have been the third GB of RAM into the fourth slot, rebooted, and no problems.  The system ran for 3 days with no problems, and surprisingly well might I add, and then on day 4, the machine kept producing error messages stating that there was an error with the system, and to reboot if the problem continued.  I rebooted the machine several times over the course of a few minutes and continued to get the same error everytime an application was launched. 

So I removed all 4 GB of the new memory, and replaced it with the machines original 512 kb or RAM, and haven't had a problem for several days now.  

Has anyone else ever experienced anything similar, and if so, was there a way that you remedied the problem?