Need some help with GPU

A molex adapter will work as long as your power supply can actually handle the card. What is the brand/model of the PSU?

It's a sl-8460btx.. i know i need a new one but this is a pre built machine and i dont think i would be able to change the power supply so now its buy a new psu or a new card and have the gtx250 sit there xD

From the specs I'm seeing for that unit it should have slightly over 300w on the +12v rails. If that's the case it should actually be able to handle the GTS 250 which averages 105w during normal gaming.

Yeah, the person i brought it off on ebay said it wouldn't power it but from what i can see from him he does not know the differences from a sempron 140 and a dual core CPU

I dont know if this will work but its worth a shot so i got 6 pin PCI express to dual 4 pin molex in hope that i can plug that into the molex coming out of the PSU and plug the 6pin into the other cable and into the GPU.

Hope this works

Even with a dual core it should be fine really. That Sempron is going to limit the GTS 250 a good bit FYI. If you don't know those Sempron chips actually are dual core processors with one of the cores locked. If your motherboard has the right chipset you can attempt to unlock the second core and odds are very good that it will work. What motherboard is in your system?