On writing to NTFS partitions:
Well the current Linux kernel drivers don’t support writing to NTFS well, there is a tool called Captive NTFS, which loads a windows filesystem driver and runs it in a (Wine-based, I think) emulation, and uses that to give read-write access to NT partitions.
I have used Captive briefly under Debian to fiddle with some files on an XP drive, although I can’t vouch for it beyond that.
Captive NTFS:
http://www.jankratochvil.net/project/captive/
On distributions: I personally use Debian; the latest network installation disk I downloaded had a friendly menu driven installer and very nice hardware detection. Debian is much easier to install than it used to be (in my opinion at least), but I don't know how it compares with Mandrake and friends.
On drive arrangements: Using a separate drive for Linux is a good way to go; you are much less likely to accidentally clobber your existing file system this way.
With Windows 98 I used to recommend installing your Linux drive as Primary Master and Windows as Primary Slave, and install the LILO (before GRUB was the standard) on the master boot record of the linux drive, with a hook to boot the windows system. This way you could always just disconnect the Linux drive and strap the Windows back to Master and have a system that would at least boot.
My Last attempt to do this with Windows XP however was unsuccessful, Windows has its own boot loader and didn’t seem to be happy about having its drives rearranged. So it looks like your XP C:, Linux D:, etc arrangement is a good one.
One thing to be aware of: In Linux systems drives are identified by there position on the IDE bus, rather C,D,E,etc, so your C: drive would normally be hda, (primary Master), Primary Slave would be hdb, Secondary Master would be hdc, secondary slave would be hdd. Note, that these include CD-ROMS as well, so your drives may not appear in quite the order you expect.
I have no knowledge of how Mandrake’s installer presents disk choices during installation, so the above may or may not be helpful.
You should make sure you have access to a bootable disk with the windows Recovery Console incase you clobber XP’s boot loader. If you have a real MS setup disk this should be on it, but if like me, you just have an OEM recovery disk (grr!), it will probably *not* have Recovery Console. Fortunately, you can download a setup disk on floppies from MS support. Unfortunately, it takes 6 disks.
On the dual boot configuration, I have to admit, I ended up taking the cowards way out. I have XP’s boot loader on the Primary Master (XP) drive and GRUB on a floppy disk. On the floppy disk it works fine and can boot easily into XP or Debian. One neat benefit of this arrangement (and probably others) is that XP’s hibernate to disk function works completely independent of Linux, so I can hibernate XP, restart the machine, boot Linux, work there for awhile, shut down Linux, boot into XP, and come out of Hibernate right where I left off.
Oops, this turned out to be a longer post than I intended. I was going to mention Captive and than quit. Oh well. Good Luck with Linux!