Bad Mbr

A serious problem and I have no solution for it. may I have your help!
on a WD600 hard disk.after working with partition magic,
I face the problem : My HD is all BAD viewed in Partition Magic!
its color is yellow (means others file system) in Partition Magic
How come?
first I was deleting a partition to make it unallocated.
but before I did I made it hidden!
of course it is unsafe!
Any way after I made this fool I face the problem and I have to solve it.
I tried to format the hard. But I face an error Message#6.
Bad Argument/Parameter!
so what?
I found out the {BAD MBR} in the formating box.
so may the Master Boot Recored is corrupted and need to be fixed.
I tried to use Fdisk command under DOS but the problem that is while I boot from a boot CD.
My pc is suddenly stops and does not continue to the DOS command it stops at a BOOTING FROM CD:..

I need to fix my MBR but I can't reach the DOS command.
when I get my HD put of PC and Boot from a CD it reach the DOS command as usual with no problem.
which means that it is a fatal mistake in my HD.
can any one give me a suggestion?
note:
in Partition Magic there are no active commands,
except format(leads to error#6).

waiting for a response!!!!

First thing you need is to be able to get to the prompt. I would try disabling everything from being a boot drive, except for the CD drive. If you still have problems then, it probably your disk.

First let me introduce my thanks for Ebot for his help.
Here is what I did to solve my problem:
First I use WD diagnostics program from western digital official site:
hxxp://support.wdc.com/download/index.asp?cxml=n&pid=5&swid=3
the program gives me three options:
Quick, Deep test and WRITE ZEROS.
Neither Quick nor Deep scan had the ability to fix the problem.
Only Write Zeros is the option that could do something.
All data has been erased, But my HD is now ready to be used.
after using Write Zeros option, My HD all volume is now unallocated. Then by using a partitioning tool, I can repartition the disk and all is well now. THANKS FOR Ebot.