Power power with ASUS HD

[exceeda88]

i have this kind of system :

GA M565 - S3 mobo
AMD Athlon X2 4800+
ASUS Ati HD5850
ASUS Silent Knight
3gb kingston RAM
WD caviar black 1 teraB
enermax 620W
5 external 90mm fan


i just bought the 5850, but my system wont start ,doesnt,that i believe is boot failure problem..
what is the problem?? is it my power supply is not enough??
or my cpu is too outdated??
is there any article i can refer bout this problem??

 

[jryan388]

Does it start without the graphics card in place?

 

[exceeda88]

before this i i use GeForce 8500, and with only stock cpu cooler..

 

[hunter315]

has it booted previously? Do you get any beep codes? If not go through the steps in this checklist, there is also a link to a site that sells case speakers for cheap.
http://www.tomshardware.com/forum/261145-31-read-posting-boot-problems

 

[exceeda88]

it booted once, and never again. but no beep codes. .
i ill go through the checklist first, thanks..