If you are going to load Win 98 you will need to use a Win 98 boot floppy.
When it boots to the floppy initially choose the option to boot without CD rom support, you won't need it until it reboots after the fdisk below.
Follow these steps
1) After booting from the floppy you will be at an A:\ prompt, type
fdisk. Depending on whethere there was an OS on there before you many get a warning about an unrecognized partition or whether it should treat NTFS partitions as...
2) Once you are in fdisk, delete the existing partitions if you want to reconfigure their sizes or simply create at least one partition for win98. You won't create your linux partitions here, only what you will want to access while in Windows. - Sidenote: as a rule when I setup a system, I create a C:\ drive for the OS and programs and always have a D:\ partition where I leave the data. Since the D:\ on a Win 98 box will be Fat32 you will be able to read and write to it from Mandrake so you can make it a large "shared" drive if you want. For example, my laptop has an 80g drive, 5 gig is for WinXP, 60 gig is for Storage (D drive), and Mandrake is then installed on the remaining with 3 partitions ( /, /home, swap). When you run fdisk and are creating a partition it will scan the disk to determine the size, don't just accept the returned result or you will be left with only one partition for the whole drive. When it returns the size you can then type in the size you want, for example 5120 will give you a 5 gig drive. If you want to create a second partition you will have the chance to do that after you have created the first by following the same step (I think the option is #1 - create new partition) and again be able to resize it when it is done scanning. Be sure to allow enough room for Mandrake (I usually install all defaults and a bunch of additional programs, my MDK 10 is about 1.9 gig initially). You can only have 4 primary partitions on a drive also, so plan out how you want to partition it ahead of time. If you are going to have 2 partions so that you have a C and a D drive, you will probably want to make the second partition a logical drive in an extended partition. You will see the option to create an extended partion in the fdisk menu. After you create an extended partition you will then be able to create a logical drive. When you are done creating your partition(s) with fdisk you will need to set the first one as active (this is where you will be installing Win98). As you try to exit fdisk it will prompt you to reboot your computer, leave the floppy inserted unless your Win98 CD is bootable.
3) Boot with the Win98 floppy but choose to boot with CD rom support this time. You will have to format the drive(s) first so type
format c: and then the same for the d: drive if you created one. You will be left at the A:\ prompt once the formatting is done, now change to the CD rom drive letter it assigned to your device (example; A:\
type E
and run setup
4) Once Win98 is installed you can reboot with your Mandrake CD1 inserted. The installer will prompt you for where you want to install. There is an option to customize, if you click that you will see a bar showing the space on your drive, you will see a section representing the C:\ drive where you installed Win 98 (and it will even have a mount point already established for that partition) and one for the D:\ drive if you created one. You can then select the unused space and create your Mandrake partitions, or click the auto button and allow it to do the creation for you. After that you're pretty much home free.
The advantage to keeping a separate c and d drive is that you can put all your personal files (downloads, pictures, etc) on the d drive and if you ever crashed your system or wanted to upgrade to 2k or XP for example, you could run their setups and allow then to format the C drive during their installation, none of your data would be touched since it was on the d drive. Same goes for partitioning in Mandrake, its a good idea to keep a separate /home partition for rebuilds. Any of the distros I've played with have always recognized the /home partition and not tried to format it during the installation so my mail and files have remained after installation.