First, my setup:
2 IDE HDD on Primary IDE (hda, hdb)
1 DVD-RW on Secondary IDE (hdc).
1 IDE HDD on Secondary IDE (hdd).
External zip drive (hdf)
2 SATA HDD's (hde and hdg)

The subject sums up what I would like to do- dual boot XP and Debian Linux on my first SATA drive.

Here's what I've done:
I unplugged all HDD's except my first SATA drive. I installed XP on a NTFS, 10 gb partition on hde1. I then proceded to install Debian as follows:
hde2: 100 mb /boot (ext3)
hde3: 3 gb swap
hde4: 20 gb / (ext3)

This WORKS. Debian detects XP and successfully installs Grub. I can boot XP or Debian. Then I plug in the rest of the HDD's. I boot, and I get a black screen that says GRUB with a blinking cursor.

So I tried something different.
Began with just the first SATA and installed XP. (This is because of an annoying problem with Windows not properly setting the drive letters - another story all together) Once XP is installed I plug in the rest of the HDDs and install Debian. Once again it detects XP without issues and installs Grub.

I boot into Linux for the first time, but when I try to boot into XP I get a messege that Windows is missing NTLDR. Only Linux is bootable.

I realize that I could install both OS's and then plug back in the HDD's one by one to find the problem HDD, so I apologize for not being able to provide this information, since I have been unable to find the time to try.

Thanks in advance to anyone who could provide _any_ insight into this problem.

You really want to have all the drives plugged in all the time during installation.

"...(This is because of an annoying problem with Windows not properly setting the drive letters - another story all together)..."
Sounds as though this is more of an issue with XP, perhaps a post on there would be better. The fact that you get the "missing NTLDR" error and are still able to boot Debian means that both grub and linux is working....just not XP.

The only thing I can think to suggest is to have all the drives plugged in, boot into Debian, create a boot floppy (very important!) which you can do with the mkbootdisk command and then try reinstalling windoze (or maybe just use the fixboot and fixmbr commands in the XP recovery console?). This should hopefully allow you to now boot into XP but it will get rid of your grub boot loader and also the ability to boot Debian. Now you can use the floppy you made to boot into Debian and reinstall grub with the command "grub-install /dev/hda". If you still have problems now then repeat the steps above and whenever you want to boot Debian just use the floppy (many people do this for dual booting, just remember to make a backup of the disc!)

I have no notion of why you would want to unplug your drives during installation. I would think that doing that and then trying to boot with the drives connected would seriously confuse the bootloader.

So how do you boot this machine WITHOUT Linux? Which is the "first" drive according to the BIOS?

You have three GIG of ram? If that is true, I doubt very much if you need any swap partition at all. Or just use a small one; OK the normal rule is 2:1, but with so much ram, three gig is a waste.

I think he has 1.5Gb RAM....still enough to do without a swap file though if he wanted. Regarding the amount of swap, 2:1 doesn't really apply to GNU/Linux, read:
http://wombat.san-francisco.ca.us/faqomatic/cache/53.html