It does not really matter how you split up both drives... but you should make sure that you have enough space for each (Win2K and Linux). Be aware that a Win partition can be used by Linux, so you could have one of these for data you want accessable to both.
You want a Dual-Boot system - use the Win2K boot loader, not the Linux one.
Your WinModem is probably unusable in Linux, unless you can find a driver - Win Modems rely on Windows software doing a lot of the processing that full modems do in hardware (so they are cheaper!).
This question is hard to answer without knowing how you want to use your system - it does not really matter unless you are really desperate to squeeze performance or are worried about your backup strategy.
Use a swap partition about four times the size of your memory, and the rest can be one big partition, or can be split up. Each partition will then hold a bit of the total filesystem.
Linux has a single filesystem, starting at the root directory, and all other storage systems and devices are mapped into it. One suggestion would be to put the root directory, etc. onto a small partition, the usr directory on a big partition (this is the software programs), the home directory on a separate partition (this is the users files), and the var directory on another (the temporary files).
Ask some more questions if this is not enough.