I had installed Ubuntu 10.04 onto an external hard drive connected by USB to my laptop:

• sdd partition

Windoze still resides on the box's internal hard drive:

• sda2 partition

I also partitioned the internal hard drive so that I have a repository where my documents etc can be accessed by either linux or windoze:

• sda3 partition (FAT32)

I'm assuming that Grub is on the external drive somewhere - as is probably now the Windoze MBR.

I'd like to be able to give my wife the ability to start the box (and boot into Windoze) when the external drive is not attached (so that she doesn't have to take the latter with her when she needs to be mobile with the computer).

What do I need to do to move grub and the MBR back onto the laptop's internal drive? Or, I suppose: What do I need to do to obtain the functionality that I'm looking for?

I'm getting somewhat more comfortable with the command line but, I still need a bit of hand-holding

IMHO best to keep things separate.
From Ubuntu, run "grub-install /dev/sdb" (presuming the external is sdb) - that will make the external bootable in it's own right. Next pull it out and boot the Windows CD/DVD. Get into recovery console and depending on Windoze version run:
fixmbr (XP)
bootrec.exe /fixmbr (Vista, Win7)

Hi.. to find where GRUB is now type at a prompt GRUB and observe this
GRUB> then type find /boot/grub/stage1

GRUB> setup (hd0) sets it up in the MBR

GRUB> setup (hd0,*) whatever partition

Don,t forget that GRUB counts from 0

Probably good to type grub man or is it man grub try and see.
Alternativly use the GRUB that you can find on the UBCD or most distros and install it...my last box had six GRUB's on it,I,m getting the hang of it so I only have two for learning,legacy 0.97 and 0.98 0.97 is the easiest to configure.,0.98 is a bit more difficult to set up.
Hope this helps a bit...

What you maybe should have done was to set usb as the first boot option choice in bios. It may have shown up as usb or a real hard drive. Most show up as hard drive. Then you could have installed linux to the usb and left the original system for wife. To select linux change boot order.

You can fix it by either making it as above or simply leave the boot order as internal and edit what ever loader (on internal) to see both but default to xp.

I'm a rude Newbie; I didn't thank everybody for their contributions (I've been away for over a week).

... Thank-you very much. It's great to have such a fantastic community of generous experts to call upon when one finds oneself stuck up to the arm pits in the mire!