The basic steps are to get a 12.7mm or thinner hard drive, a "flipped" IDE cable, and a bios chip.
You use a 2.5-3.5" adapter and set up the 2.5" drive on a desktop computer so it will boot, then you copy the Win98SE cable files, the via 4in1 drivers, and mode.com onto the drive.
Plug in the cable & drive using you choice of mounting methods.
Swap out the bios chip, observing polarity. You don't need a chip puller. A small flat blade jeweler's screwdriver worked into the open corners will get the old chip out. Just use finders to press the new chip in. Polarity dot on the shoulder of the chip goes toward the modem. Backward=bad smell and dead IO.
Plug in a standard PS2 keyboard, boot up and as soon as you see light start hitting CNRTL-ALT-ESC to enter setup. Change the boot sequence to C-Only. Save settings & exit. It should now boot to the C drive.
Type mode co80 and run setup to install Win98SE. Load the VIA 4in1 drivers and you will have a Win98 Machine. If you want ot get wild & crazy you can boost the machine to 128M ran and a 450Mhz K6-2P with a little soldering.
It isn't as easy as it sound, but a lot more enjoyable. Prepare to get addicted