IBM 486DX2-50, Red Hat 7.1

Earlier the working system is a Red Hat 6.2 Linux, which I don't have the CD with me anymore. Red Hat 7.1 seems to be a good distribution. After I boot up the red hat 7.1, it complains 'not enough memory to install'. I have 16m of ram now. I still have some spare ram with me. I switch it over, the machine is too old, it can't support the newer ram. I read some the IBM 450DX2 ram specification, it can support up to 64M. I am stuck here now.