Recently I upgraded my Redhat 7. 1 kernel from 2.4.2 to 2.4.9, then changed lilo to boot form new kernel. My problem is, my memory down form 1 GB to 900+ MB, although the old kernel work fine with 1.8GB swap. How can I resolve this.

ps: sorry for my english

you need to make sure hi mem is enabled when you compile the kernel