help!

I recently purchased a dell dimension 8400 with a single 160gb hd. I thought it would be a good idea to divide the disc in 2 partitions, and thus did so with partition magic. However, i found that there was another way to to this which would make it all tidier, so i told partition magic to merge the two partitions. The computer restarted, as it was supposed to, but couldnt boot. I get the message: "loading pbr for descriptor 2...done." and then a blinking _  with no further action.. I then insert the windows disc, in an attempt to reinstall it, but it says it cant find a hd installed.. Now, i am pretty clueless as to what to do. I've tried inserting another ide hd, booting from it, but it didnt work, i also tried to make a sata driver disk, but couldnt get that to work.. I need help!