Question Monitor showing blank screen with no post when installing new gpu

[Avalon DJPon-3]

I have bought a new gpu for my pc but when its installed to the motherboard, there is no post and only a blank screen. I've tried uninstalling all the graphics drivers and that didnt work. I unplugged all devices including the hard drive and that didnt work either. The monitor is connected to the card itself so it does show signal but just a blank screen. I've been searching all over the internet and some people have the same problem and solved them but they dont work for me. If anyone knows what could be wrong then please help. The card I'm trying to install is the M0KV6 AMD Radeon HD6450 1GB SFF. Thanks in advance

Specs
Intel(R) Core (TM) 2 Duo CPU E7500 2.93GHz
4G ram
465GB storage
Model - 0C27VV

 

[cin19]

Model - 0C27VV

Did you have the dell PC? If yes,

1. Buy other PSU, if the PSU in the dell pc is less than 300W.
2. Update the BIOS, you can get the BIOS from dell website.

I've been searching all over the internet and some people have the same problem and solved them but they dont work for me.

3) If you did try these ( step #1 and #2), return the HD 6450.

 

[Metal Messiah.]

Is this your MOBO ? Are you booting in Legacy mode ? have you tried updating the system BIOS ? The DELL OEM PSU might also the culprit here. Depends on the quality of the unit as well.. You need a better PSU for the HD 6450, if your current PSU is insufficient to power the video card.

Clear and reset all the CMOS/BIOS settinsg to default, if required. Can you boot your system via the onboard graphics ?

http://www.ascendtech.us/dell-c27vv-optiplex-780-motherboard_i_mbdelc27vvox780.aspx