Are all the power connectors connected(if needed) and is your drivers up to date?
On top of that try a motherboard BIOS update, then list your FULL PC stats including case and power supply so we can try diagnose the problem.
If you tell us what country your from(I assume US) and your price range for any corrective fixes it may also save you and us some time in the future.
Compaq Presario SR5550f
AMD Athlom 64 X2 Dual Core Processor 5400+ 2.80 GHz
3.0 GB DDR2 RAM
2 LightScribe DVD Writter
Two 500 GB Hard Drives (1TB)
One PCI express x16
Two PCI express x1
One PCI slot
250 watts power supply (total)
Any reasonable price to repair.