ATI HD5770 having a boot up problem and doesn't show any post screen >_<

hi there.

i was going to put on windows 7 on my computer which is 2 years old now. a rough spec list is as following:

core 2 duo 2.66
2 gb ddr2 667
xfx 7600 gt
430w thermaltake powersupply
2 dvd roms
1 sata hdd (300 gb)

after installation i noticed there were weird color lines and dots on the screen which i never noticed with xp before. I finally figured out the graphics card is not working properly as i tried another card from my frd and the dots and lines disappear.

So i bought a sapphire ati 5770 and put it on. The probems of the lines and dots didn't come up again but then it "ignites" 8 to 10 times before it starts up properly and always freezes at the windows start up screen.

but then when i put the old card in everything works perfectly (except for the lines and dots problem) i then drew the conclusion that the other part of the computer should be working properly so i am lost from here. >_<

and when i pulled out the old card and put the new one in again it stops showing any post screens and only show images when the windows has started up. and i can't even change the resolution from 640x480...

i tried with another new 450 w powersupply and same things happened so dun think it's the power supply problem. I am also pretty sure the other parts of the computer are good coz they work perfect with the old card. i also tried to clear bios and didn't work. i uninstalled the old card driver too didn't work.

could anyone help? >_<
to summarise the 2 problems i have now are:

when the 5770 is in it ignites 8~10 times before producing that beep sound and starts booting up.

and nothing comes on screen until windows starts up. And can't change the resolution from 640x480.

thanks a lot. >_<

 

5770 will require more than 450w, most likely stability issues down to such low power psu. Also what is the brand of the 450w psu that you tried using?

 

well it does say that but i doubt it's the cause...because i've seen people booting it up with a 380w psu. Also, i tried to unplug most of the parts of the computer so only the essetial parts are on (mb, cpu, hdd and the card) same problem appeared. I would have thought that 450w requirment takes into account of a sort of "loaded" system...

btw, i did some further testing which shows that the new card is completely good as i put it into my dad's computer (where that 450w psu i used before came from!) and it worked. So "broken card" is out.

it's a gigabyte 450w not too sure about that model but it's a good quality one.

thanks >_<