Please help me! I have kernel panic on boot

Question

Greetings.
I have to be honest with you and tell you that I have a problem with my iMac computer. I'm a big fan of Apple products, especially Mac computers. I live in Bosnia and Herzegovina, where there is no Apple store, and that's why I bought my iMac computer in Croatia that was used that had a "kernel panic" error. After several failed attempts I managed to install "hazard OSX Snow Leopard" and the computer boots up normally but when it goes to shutdown freezes and shows "kernel panic" and says "you need to restart your computer." When I installed OSX everything is working normally, but I have no sound, the computer continues to shutdown shows "kernel panic" or "system uptime in nanoseconds ..." freeze. I bought the original OSX Snow Leopard DVD because I want to have a legal iMac computer and legal software on it. When i try to boot from original "OSX Snow Leopard" i get "kernel panic" fast after Apple logo appears. I try other discs but i get same problem. I try reset pram, nvram, SMC, i try another HDD and no help. I bought 2 original memory sticks  2x2Gb in Germany and when i put one or both , turn on Imac but no startup chime and no picture.
Please help me solve this problem. thanks
My iMac computer configuration is:
6.1 iMac 2.33 GHz Intel Core Duo 24 "White
S.N. W8******VGP
Memory: 3GB, 667 MHz DDR2 SDRAM
OSX Snow Leopard 10.6.2
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Answer 1

I did all the tests with the program Tech Tool Pro and post pictures to see if everything is fine with my iMac computer. If there is still any advice please help me. I installed Snow Leopard Biohazard and boots properly except when off or reboot blue screen freeze up and only one point where the mouse is.