From what you have posted I don't see how you could have started an installation. More specifics on exactly what happened might help.
I had a similar problem. I tried to do a dual boot with Windows XP and openSUSE. I had done such a thing before back in the day when I was running Win 98SE and I dual booted with Red Hat, but I was on dialup then.
This time I tried to dual boot openSUSE with Win XP, but I was connected with a wireless dongle. When I went to run the ISO disk that I got, since I couldn't connect to the net through the dongle, I couldn't access the repos I needed to install SUSE. When the installation program ran from the ISO disk, I think it overwrote my MBR for Windows, since every time I tried to reboot I got the black screen with "error loading operating system".
The only way I managed to get to where I am now running Linux was to physically connect my PC to the router with a cat5 cable.
Maybe the starter of this thread is on a wireless.
You here at LQ should start a pinned thread: Do Not Try To Install Linux Unless You Have A Physical Connection!
I have tried (with much expert advice) to get my wireless dongle to work, and it has always failed.
Please tell people this before they fry their Windows trying to dual boot.