Still no picture

Hi, a mate brought his comp to me with no pic , i have tried all tests {rubber,processor,ram out} but to no avail ... i have now put a new mobo in ASUS P5PE-VM , it has 1gb ram {1 stick} .... is there a chance that the power supply is not working correctly ? having looked at the mobo manual, which i found online, it says it needs a minimum 300w to power it , the one in comp is min 250w max 300w ..... i have taken the h/drive out and put in my external case and am able to access files on it {so think thats ok} ... there are no beeps with or without ram in.... any advice from anyone greatly recieved ..... also is there a test i can do to make sure power supply is working ok ... many thanks in advance for anyone that can help


comp is an E.S 102
celeron D336
80gb h/drive
xp pro
DDR Ram