The 260 I used a while back was from PNY but should function the same.
First I would make sure the fans are kicking on the graphics card. Sometimes they can be hard to hear over the other fans in the system so power it up and grab a flash light. Make sure the fan is on. You can also try placing your hand near the little vents on the back of the card (where the video outputs are) to make sure you feel a slight draft blowing out of there.
Next, I would check how you have it connected. The 260 has two dual link DVI and I think an old style S-Video connector. The best way to go, if your setup supports it, is DVI on the card to DVI on your monitor. Most modern monitors will have a SVGA and DVI input these days. If your monitor has a DVI plug on it (that’s the one with a 3x8 grid of pin holes with either a horizontal hole or a horizontal hole with 4 pin holes around it).
Then, check the monitor. Some monitors don’t like to auto-detect what’s connected if they have both VGA and DVI inputs. See if there’s an input select button on your monitor and make sure it matches how you connected the card to the monitor. VGA may be called ‘analog input’ and DVI may be called ‘digital input’ by your monitor. Look in the on screen menu for the monitor if it has one, sometimes that option is buried in the menu.
If all that check out look in the bios for your motherboard. If you have on-board video or a second video card installed try connecting your monitor to that card (with the 260 still installed) and see if you get any output to your monitor. If you do, then your bios may be forcing the use of that other card instead of the 260. Look in your bios settings and see if there’s is any setting for using on-board or PCI-E for video. Don’t know the make/model of your motherboard so the bios may call this setting anything. Look for something about on-board and see if you can force it to PCI-E instead of auto, on-board, or maybe integrated.
If all else fails there may possibly be something wrong with the card itself. Is there another computer you could put it in to try it out or another PCI-E card you could try putting in this computer to make sure that the GTX 260 itself isn’t bad or burned out in some way.
Let me know how those steps work out for you and we can take it from there.