Yes, I did install both OS together ,but, then I was lucky,I had no idea what a mount point is , i just selected "/root" , "/home" , "swap" thts all.

But, then after I partitioned the 1st partition of my IInd HDD , then RedHat didn't run it said "Kernel 2.xxx...blah , blah...panic". Possibly you altered your MBR.
Now. what the hell...