Question My computer stucks at HP logo screen.why?

ALI_6_

Honorable
Oct 18, 2015
11
0
10,510
I have a pre built HP pro 3400.
I5 2400, 6gb ram, ssd and hdd, hd 7700 series card.

I changed my psu to Corsair VS450(used) and gpu to Asus 750 ti OC(used).

With the new gpu computer stucks at hp logo screen i.e bios doesn't load up.cant access bios , boot menu, startup menu and it beeps after 25 seconds but when i put the old gpu(amd hd 7700 series) back it works just fine.

Thank you for your time.