Hi Ron,
You will need to obtain Commercial Software to hadle the partitioning for you, unless you wish to Wipe that Windows 98 installation clean and start over. Your Windows 98 Startup diskette will contain a utility called FDISK which will perform drive partitioning for you, but it cannot resize an existing partition. It can only delete partitions and create new ones.
Method 1
Boot from your Windows 98 Startup diskette, and at the A:> prompt, type 'FDISK' (without the quotes). Use the tool to delete the partition, and then to create a new one of the size you require.
When finished, proceed with the installation and setup of Windows 98.
The reboot from your Windows Server 2003 CD, and use the install routine to create a second partition and install Windows 2003 Server on it. the installation will create the dual boot for you.
Method 2
Use a Commercial utility profram such as Partition Manager to resize your existing Windows 98 partition, and create a new partition in the remaining space.
Reboot from your Windows Server 2003 CD and install to the new partition. The dual-boot will be created for you as above.