Long story on this one. I am in the military. I came back from Korea about 6 months ago, when I received my desktop (which had been shipped in my household goods) I couldnt get it to work at all. I took it to a few people who were pretty tech-savvy to see what the problem once once I realized the problem was above my level of computer repair knowledge, I was informed the motherboard had most likely shorted out (tried different RAM, Processor, Power supply, and HD). I took my loss and eventually replaced it with an nVidia 730a motherboard.
Things seemed to work fine (for about 10 minutes) until the system crashed. The crash turned the screen a random color (which appeared to be influenced by whatever color appeared the most on the screen). I could not find any correlation between anything specific the computer was doing and the crash. I pulled out the video card (gForce 8600 GT) and ran it off the integrated 8200. Same problem. I changed out the RAM with brand new sticks, same problem. I was running Vista x64 at the time. I came across a spare HD which had an old deactivated version of XP on it. I replaced XP on that with 7, and it seemed to work at first, but I wanted to use my original hard drive since the spare didnt have a SATA port and it was a real pain to connect the spare hard drive and the ODD via IDE due to the space in my case. So, to make sure that if it was a problem with the original hard drive, I used Killdisk on the original hard drive before reformatting it and putting 7 on it, to make sure no potential viruses or anything remained on it. I then restored the backup HD with the eMachines version of XP (which will work for me for another 30 days now) 7 seemed to run fine on my original HD for a while, but then started freezing up (without the strangely colored screen). Fed up, and thinking it must be a hardware issue on the original HD, I went about trying to put 7 back on the backup HD. Lo and behold, partway through the installation on it, I get the freeze with the random colored screen before I can get very far into the installation. Power supply is kinda old and that is the only thing I havent changed out on it, but would the power supply cause the system to freeze like this?
Seems that something must have happened during shipping if it was working fine before. Probably the things that get damaged the most in shipping are the HDDs.
That being said have you checked your case close enough to see if its disorted in some way? That could explain a shorted M/BD. Did your graphics card get knocked loose or completely out of its socket during shipping that you didn't catch until you tried to turn your PC on?
Also the HSF on your CPU could be not seated properly as well thou that would have been corrected with the M/BD replacement or should have been.
Lastly did you have the M/BD replaced by a computer shop or friend or did you do this yourself? No insults implied just trying to help figure out what happened to cause this thus leading to a better solution.