I recently bought a new graphics card, it is an Nvidia Geforce GT 640, it was the same as my other one, well it is the same model. I was originally using an Nvidia Geforce GT 640, but the fan stopped working so I replaced it with a brand new Nvidia Geforce GT 640. This one does actually look different, on the box it says factory overclocked and this one also has a much bigger heat sink fan. It recommends atleast 350w power supply, and mine is exactly 350w I have 16gb ram windows 8 intel core i5-3350p. My problem is when I start up the PC with the new Graphics Card the monitor just goes to sleep, nothing else happens. It doesn't bring me to my desktop or anything I have the monitor connected straight to the GPU... PLease help.
check your connections, try to see if putting your old card back in will work. then you will know it has something to do with the new card. im suspecting that your power supply isnt enough. even tho it's rated for 350 watts it might not exactly put out that much (retailers estimating up)
I checked my connections about 20 times, lol. And everything works like usual with my old graphics card.
Check your CMOS settings in the BIOS to see if it is trying to use the onboard chipset instead of your card. If that doesn't work, or isn't wrong, then I'm not sure there's anything other than to return for a refund or new card.