By recovery disc you mean no Windows CD?
Ok, lets see:
Have you made any changes recently?
Did you have any error messages recently? Any BSOD ?
Can you go to Last good known configuration or Safe mode by pressing F8 while the computer starts?
Try Last good known configuration first!
Or you can only access BIOS? (if it's an Acer the F2 key works)
I you can go to your safe mode try a System restore to a previous date, or try different startup types with msconfig (start>run type msconfig).