OK, so here's the thing, I have 3 HDs, C, D & E. I had Xp installed on C then, after I added the E drive I installed Xp on D and I want to ditch the C drive. but If I remove it it won't boot at all. how do I make the D drive the primary boot drive?

You have to move the bootloader to that drive. You could try taking the C: drive out, using an XP repair disk, and seeing if that works.
I'm sure there is a 3rd party way to do this too, I just don't know of anything off by heart,

I wound up having G as my boot drive on my secondary rig, and it was a combination of using two different computers with XP installed and swapping the drives so they were both in one PC at one point. I don't remember the exact steps, though.

A word of caution, there are still programs that hard-code the C drive into their file operations. I had to virtual mount a folder on G to act as my C drive so certain programs could run.

I would say just reinstall on the C: drive to make things easier honestly.

Or you could take the drive out you want to remove, boot into recovery console from the CD and type /fixboot [hit enter] /fixmbr [hit enter] /bootcfg -rebuild [hit enter] in that order. It'll detect the new windows installation and create a new bootsector.

So wait, windows has been installed to D drive? Is BIOS pointing to the right drive to boot first..