I have a dell dimension 8250 that I've had for quite a while. Up until now I've been able to fix all of its problems but I was swapping out a hard drive and I accidently pulled out half of the power cord and the computer short circuited and it took about 5 minutes till I could boot it but when I booted it it couldn't find my hard drives at all. I've tried doing a forced IDE config I've switched the hard drives and switched the power supply. The bios menu still shows that I have all my ram. I've also tried taking out the little battery and vacuuming out my system and power supply. But I've only been able to get 2 hard drives found on a vista installation disk but it couldn't install onto them. And now it can't find my disk drives now.
I would really like to know what's going on and how to fix it.

I strongly suspect you have fried your controller, or the drives. Have you tried another drive to see if it is recognized?

When you say that you pulled out half of the power cord, do you mean the power cord that connects to the Power Supply Unit (PSU) at the back of the computer? If that is what you are saying then it may only be your PSU that has been damaged and not the rest of your computer.

I've tried different hard drives and disk drives and even new cords but it still won't work. No it was the cord plugged into the hard drive

Do you have another PSU you could try? I wouldn't be surprised if the controller on that one drive has burnt out, typically when they're shorted you see the chip glow red hot. (though only as it is happening) But, I have doubts about the other drives dying too.

It's up to you, but I would recommend trying another PSU if you have access to one.

I Reyes a new psu and had the same results. What glows red is its shorted? I couldn't see anything.

You have most likely damaged your chipset on your motherboard. With a fault like that, the only options you have is to take it to a repair shop or replace it with a new computer.

Sorry, sorry, sorry, the comment about the chip glowing red was just my recalling a past experience. It wasn't relevant to your problem.

At this point I'd strongly recommend getting hold of some diagnostics software and give it a thorough check over, UBCD is a popular diagnostics option, but there are more out there.

How will I be able to run it on my computer?
Is there any major stores that will do it for free or cheap?

Is there any major stores that will do it for free or cheap?

Without knowing where you are in the world, that question is impossible to answer.