i have a few questions about my pc, i bought a gaming computer about 4 months ago   from the day i got it i uploaded it an from the moment u push the  on switch it takes a good 3 min to get to the desktop, well within the past 2 weeks  i will be doing random things ONLINE,or PLAYING a game or jusst chatting an the entire computer just goes off  kinda like when the power goes out at ur home but this is only the pc  i have cleaned the dust i replaced the power suppy  i have done a virus scan and everything i can think of, after i did the power supply  it let me do whatever for a good 8 hrs, then did it again i went to boot it back up an it would get so far an shut off so i let it sit i am on a mini laptop now the only thing hooked up to the desktop now is the power cord i turned it bk on an its on now  just sitting therelisted below are my specs

CyberpowerPC Black Gamer Ultra GUA250 Desktop PC with AMD Quad-Core FX-4130 Processor, 8GB Memory, 1TB Hard Drive and Windows 7 Home Premium


AMD Quad-Core FX-4130 processor
3.80GHz, 4MB L2 Cache

8GB DDR3 SDRAM system memory


1TB SATA hard drive


24x DVD+/-R/RW drive


10/100/1000Base-T Ethernet


NVIDIA GeForce GT 610 Graphics
Normally I would start with checking the Power Supply but as you said you have replaced it.

Was the replacement PSU a cheap unit?

Are you able to tell us the wattage rating on your PSU?
I realise you only have a GT610 card in the machine but it is important none the less.

Have you tried running a monitoring program such as Speedfan or Coretemp?

www.alcpu.com/CoreTemp/‎

This will allow us to ensure heat is not an issue. When you cleaned the dust out, did you also remove the heatsink from the top of the CPU at all? it is possible that there is limited contact to the CPU causing a slow thermal creep up to shut down due to temperature.

The last thing is the power quality in your household. Do you notice lights dim or interference with any old CRT style Televisions or monitors? It may be that you need a UPS or equivalent in order to keep stable current and voltage going to the PC. Also try another power outlet directly into the wall, TAKING out any power strips or adapters.If it's 4 months old I would be exercising my warranty - that is, after all, why you paid for someone to build it for you.Honestly, DOWNLOAD speedfan and check your temps, make sure its not an overheating issue also, install CPUID, and post your voltages as well so we can see what its pushing at.