New gfx card, computer doesnt start

[unnamed1234]

hello. after installation on motherboard new gfx card - asus radeon 5750 1GB ( EAH5750) gddr5 40nm 86Watt pc doesnt start, monitor doesnt turn on, diode is blinking, screen black, no sounds that something is going-hdd silent, off-button doesnt work.
i searched in web about it.
on the box there is:
"recommended system requirements:
-2gb system memory or more for best performance
-motherboard with free pci express slot and correct pcie chipset driver
-microsoft windows xp/vista/7
-a minimum 450w system power supply
-a pcie supplementary power connector."

-pc has 1gb ram, here they are recommending or demending 2gb
-hdd is silent so i dont think about OS- there is xp 64 pro sp2
-power supply has more - 550w, but i disconnected all hdd,fdd,keyboard,mouse (only power and monitor cables remained) and still nothing...
-ive connected pcie supplementary power connector (6pin) to the card ,the card has probably pcie 2.1, motherboard i guess 1.0 (i have it since half of the 2005) hw info program shows also 1.0, but ive read that on 1.0 slot the 2.1-card should work.
untill this moment to the mb have been connected power supply 20 pin and was ok. now i plugged in additional 4 pin and in the other place of mb another 4 pin cable.- didnt helped, with radeon x300 works ok.

-bios reset -nothing, ive loaded old default bios version "F2"-nothing. ive downloaded latest F9d (i had F9c)-helped not.
i put ram memory in the recommended 1,2 slots closer cpu (it was in 3,4), i runned pc also with 1 dimm module 512 mb (64 bit mode),i put in also third older module 512mb (double-sided) but in manual there is that mb doesnt support such configuration(3 modules 64bit) they say to put 2 modules (128bit) or 4 in all 4 slots- on 5750 -no change.on x300 pc turned on and printed on screen 1.5 gb 64bit instead 1gb 128bit, but later didnt turn on only after i disconnected that 3rd module.
untill this moment monitor was connected to the x300 dvi through dvi-dsub connector (it was with gigabyte x300 card) . with the new card there is also similar connector (has lower number of pins) and on it x300 works also. on 5750 there is no difference if i connect with this or the other connector, to the 1st or 2nd dvi of the card. there are also hdmi and hdcp ports but i have nothing to connect to this to check out.
ive cleaned pcie slot on motherboard-doesnt helped.
card fan works. i saw somewhere on forum somebody solved the problem buying stronger power supply.in the other case loading non-standard version of bios helped. i can try different things , the mb has dual bios- but im not sure the recovery will activate when needed.
in bios there is position giving possibility to change pcie voltage.it is set on "startup" and there are also values (lowest to choose- 0.800 V), maybe i should set on of this values instead.maybe new card needs higher value.
reset button and power button are properly connected.
have i buy 2gb ram or more?maybe motherboard with 2.1 pcie?
here are opinions about this card and they are positive but all users have in their computers 2gb or 4gb ram.
1gb- is it too small amount of memory?
http://www.komputronik.pl/index.php/product/86314/Podzespo_y_PC/Karty_graficzne/Radeon_5750_Asus_1GB_2xDVI_HDMI_DP_PCI_E_.html

configuration:
monitor crt samsung syncmaster 753 DF 17"
mb gigabyte nforce4ultra (k8 triton, GA-K8N Ultra-9),
cpu athlon 64 3000+ venice 90nm socket 939, 512 kb cache(1.4 v,1809 mhz,fsb 201,HT 5x=1005mhz)
memory 2x kingston 512mb pc3200 ddr 400mhz(201mhz(402),fsb:ram 1:1)
gfx gigabyte radeon x300 128mb PEG
power supply 550w (techsolo, TP 550W)
2x hdd WD 80gb,1xhdd samsung 250gb

 

[gkay09]

^ PSU might be a problem...How old is it ? And generally low quality PSUs deliver lower power than the rated value...So at max it would output 300-350W of power...And also if the PSU is old, its efficiency decreases and also the power output...

The amount of RAM doesnt matter much...1GB is also fine...

 

[jyjjy]

Yeah, if I had to guess it's your PSU. Sounds like your system is pretty old and PSUs tend to degrade over time. It may have been ok when you first bought it but possibly at this point it just isn't powerful enough.
You may also just have a bad card. If at all possible install it in a different computer with a decent PSU and see if it works. You may just want to send the card back anyway. An HD5750 is more powerful than a single core 3000+ can really use and 1gb of ram certainly wont help. You'd be better off saving some money and grabbing an HD4670 for half the price + another gig of ram. The HD5750 would be wasted on that system even if it was functioning.