I assume you have one harddrive, connected as first hd on the first controller, and which is therefore named /dev/hda.

A second device on the first controller would be /dev/hdb, the first dev. at the sec. controller /dev/hdc and so on.

I assume further, that you like to have a partition for win, a normal one for linux (type=83), and a swap-partition for linux (type=82).
For win98 you will use a vfat-partition (fat32? not sure, type=c).

For the size of your partitions you decide by your needs - if you have no idea do it like this: your physical RAM * 2 for swap, 50% of the rest for win98 and linux.

To partition the drive, you call
Code:
fdisk /dev/hda
You will get a prompt which shows that you get the list of options with 'm'.
I would start 'p' - print partition-table.

Depending what you get as response, you may delete the partitions listed there.
Create a new partition (primary) for win98 as first partition - which will be '/dev/hda1' for linux and 'C:' for windows.
Toggle the bootable flag for this.
Create the two linux-partitions.
The list of types you get with 'l'.

If you're unsure, you may always leave the program with 'q'. As long as you don't hit 'w' like 'write' - your changes aren't made.

After partitioning, you have to format the partitions.
mkfs.reiserfs for the linux-partition (/dev/hda2).
If you can format the win-partititon with the windows-install medium, I would prefer that.