Check if you have a bootable cd or floppy and if you have set hdd as the first boot device.
agreed , very much but this first step doesnt necessarily a boot floppy.
Invalid system disk replace the shit means check your bios pressing delete several times when u hear two beeps indicating the system has started.
Now goto advanced settings and check for the first boot device. If its ok , then check using Esc+Tab.(press the sequence repeatedly)
If u see the hdd is detected(some info like your hdd brand with serial no) for example if its seagate is goes like ST XXXXX where x is number.
If its not detected , agin press delete enter setup and goto cmos settings and check (the four devices primary master/slave and secondary master/slave)
If yo hdd isnt detected, then config manually.
If this too is ok, see in Peripherals tab for a option called Primary IDE , if this is disabled this can also cause such a error. These are three common problems faced with this kinda error.
I DO NOT RECOMMEND ANY OF THE ABOVE TO NOVICE WINDOWS USERS, ITS FOR INTERMEDIATE USERS WHO HAVE ADEQUATELY PLAYED WITH WIN OS FOR A WHILE. IAM NOT TO BE HELD RESPONSIBLE FOR THE PROBLEMS FACED BECAUSE OF DOING THIS. I AM JUST SUGGESTING THIS SOLUTION , NOT FORCING IT
Any questions plz get back to me or pm me.