How do I fix my compaq 615 laptop?

I've used it for sometime now but yesterday I tried to booth it, the system freezed. The power LED indicates that the system is on the WLAN indicator is equally lighted. But the screen is blank. After few seconds, the caps lock LED blinks 5 times and that's it. It remains like that (i.e. the blank screen, the power and WLAN LED). The processor fan is equally on. What could be the problem and how do I fix it?