I got some good advice from Skateman.
>>Unplug the powercord of the PSU
>>Then push the powerbutton.
>>Then plug the powercord back in and try to turn it on.
This solution didnt work.
>> Remove and reset memory from motherboard.
When i did this i got my x5000 to boot again. Maybe there is something wrong with the ram memory?
A big thanks to Skateman