A Reeaalll Tough One!! (Pc wont start properly)

I think only the hardcore computer geniuses will be able to answer this, but any useful input from anyone would be greatly appreciated.

On my other PC, when i turned it on i recieved the following message:

Windows XP could not start because the following file is missing or corrupt: \WINDOWS\SYSTEM32\CONFIG\SYSTEM

And nothing would happen, it remained in dos mode

So a friend of mine told me a wire could be loose, so i opened the PC and unpluged and re plugged all the wires into the hardrive and mother board.

Now when i turn that PC on it doesnt detect master or slave or anything (dont really know what that is?)

and leaves me with this message:

Disk boot failure, insert system disk and press Enter

So i put the cd in that came with the PC that says Boot cd for recovery (or something like that) and press enter, the PC restarts and then the same thing happens, i get the

Disk boot failure, insert system disk and press Enter


Can anyone please give me some hints as to what should I do? Im a real idiot when it comes to PCs so if anyone can help please can you give step by step instructions. Any help would be grreeaatly appreciated.

 

"So a friend of mine told me a wire could be loose, so i opened the PC and unpluged and re plugged all the wires into the hardrive and mother board."

Sounds like somethin is loose or the bios was changed to a different boot device?(do the hd lights come on or???)
Hopefully the above was done with power off and unplugged
And last but not least are you sure you did not bend over a pin (did it myself) on the hd --

h