BSOD on startup

[Achileon]

Hi..I'm new here and have quite low knowledge about computers..I recently assembled my desktop and I'm having constant blue screens on start up only whenever I boot up after a long interval of time(say 3-4 hours or so)..so, I gave my cpu to the vendor, from where I purchased, to test for ram, graphic card and HDD but he said that my cpu was fine and there was no problem.. my desktop config is

Processor Intel(R) Core(TM) i5-2300 CPU @ 2.80GHz
Memory (RAM) 4.00 GB
Graphics ATI Radeon HD 5500 series
Memory Size 2551 MB
Hard disk Size 160 GB
Windows 7 Professional

And below I've attached my last 4 dump file..Please Help

Thanks

 

[Tmagic650]

"whenever I boot up after a long interval of time(say 3-4 hours or so)"... This may be an overheating issue or a failing/sub-standard power supply. The minidumps are "all over the place" so it is difficult to pinpoint a problem using them