Disk boot failure, insert system disk and press enter...?

I'm confused! Our OS crashed on our computer, and my stepdad reformatted the hard drive. Last night while it was at my mom's, they were able to get it started and going online with some antivirus software installed. Well now at home, I'm getting this error message: Disk boot failure, insert system disk and press enter. There aren't any disks in the drive, and we don't have the OS disks (my husband left them at my mom's when he picked up the computer) - are we temporarily screwed?

Disk boot failure, insert system disk and press enter...?computers

You're temporally screwed until you get the Windows disk(CD) that came with the computer. Once you have it, boot into safe mode and set master boot to CD drive and exit. Shut down computer. Insert CD in drive bay and restart computer. Once computer restarts, it will give you some options...choose Repair. Follow any prompts. You may have to restart PC again.

Disk boot failure, insert system disk and press enter...?hijack this

Unfortuantely, the disk that your computer is referring to is the hard drive disk. The OS is having trouble reading the hard drive instructions and thus the error. What you will need to do is buy a new hard drive and install it to fix the present problem. No big deal, just a pain in the *** is all. And yes, you are temporarily screwed until you pick up another hard drive.
You may not necessarily need a new hard drive, it could just be formatted wrong (a software problem). This seems plausible to me since you said your stepdad just completely reformatted the drive. However, since you said it was working a little while ago, it's also possible the drive is physically damaged. You should be able to test the drive's integrity to some extent if you put a DOS-based boot disk or CD in, and use FDISK or other tools to look at the drive. However, this is a little complicated to explain in a short answer like this. If you do get another drive though, you will have to go through these same steps, so it might be worth it to look up FDISK, FORMAT, etc and simple DOS commands and play with them on the drive you have now before you go buy another one. There's a chance you could fix it without having to buy anything at all. If the DOS stuff is too complicated for you, you could try putting in the "recovery" cd which might have come with your computer. Note that both these options will likely erase everything currently on the drive.