Win 98 installation

I have a Pentium computer 400 Mhz. I disconnected the hard drive and put another hard drive on it to have it fdisked and formatted. After I reconnected may hard drive the computer will not boot I cannot even get into setup. I took the hard drive outand fdisked and formatted it from anothe computer and put the hard drive back into my Pentium II and when I install the win 98 operating system it makes c: the ram drive and it does not recognize my hard drive at all. I can not even get into setup to try and rectify the problem. The computer is also very slow. Has the BIOS or the motherboard been reconfigured in some way by using my Pentium II to format another hard drive. Please help