P6 2200ec - windows 7 do not start after graphic card change

Hi,

I have HP paviloion P6 2200ec - windows 7 64-bit

(PSU changed to 450W) 

I changed the original graphic card Nvidia GT640 to NVidiaGTX650Ti.

Unfortunatelly windows 7 do not start after the change - I can see the start screen, but no reaction to ESC button. (6 -pin cable pluged, fan on graphic card rotates)

When I put back the original graphic card, everythig works fine.

The problem already deiscibed in this topic 

http://h30434.www3.hp.com/t5/Desktop-Hardware/New-graphic-card-3-beeps-and-windows-won-t-start/td-p/3073595

But the solution is to chage the motherboard (this is someting I do not want to do)

Can anybody advice what to do?

Or to recomed a higher level graphic card which will work in this PC.

Thanks