p60-lba-problem-850mb-harddrive

i finally found the solution with the mouse-problem: special com1-cable!
now i have a 850mb-hd with win98a already installed. its a dell xps 160(micronics m5pi.
in the bios there is no possibility to overcome the 504mb. original hd did not exceed this barrier. how can i use the full 850 without loosing my installed windows98a. diskmanager-tool is a good idea. what should i do exactly?