Computer Won't Start >_<

I punch the on button… It beeps, the ‘checking ram thing’ comes up and checks the ram… it says “Detecting IDE Drivers”. Sits on that for 30 mins. Then says:

INVALID BOOT DISC PLEASE INSERT SYSTEM BOOT DISC.

help!!

system =

P4 2.6ghz
1024mb RAM (2x512 dual mode)
Saphire Radeon9600XT 256mb
Windows XP pro
…uh I can’t remember the rest right now, but thats the basics.