Clarify the boot sequence in Windows XP?

This is my first time using cnet forums, and not everything is clear to me yet, such as where is the search function? Searching is the only effective alternative to spending (hours) reading through posted headers and messages. (I have sent a message to the system operators on this, so please don't answer it here.)

OK, on with it. I am using Windows XP, service pack 3. I have to start with a general description of my system, which I will keep as brief as possible. I started with XP installed on the primary disk (disk 1), and later installed Ubuntu Linux on the secondary disk (disk 2). After that, I installed Windows 7 on disk 2, using the standard procedure from the install disk. So far, everything is hunky dory. I can change the bios to boot first from either disk 1 or disk 2; currently, it's booting from disk 1.

Now, if I boot from disk 2, it goes straight into Ubuntu Linux. No big problem there. When I boot from disk 1, the boot manager gives me the following two choices, listed from top to bottom: a) Older operating systems, and b) Windows 7, with choice b) being the default. Here's the active content of the boot.ini file:

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional"
/NOEXECUTE=OPTIN /FASTDETECT

This, as far as I can make out, is what governed the boot process BEFORE I installed Windows 7 on disk 2, since it contains no mention of the alternate login. My guess is that the Windows 7 installer modified the boot process somehow on disk 1 to make Windows 7 the default (timeout) operating system. The question is, where and how? What I want to do is re-format disk2, after removing any partitions it may have on it, but I want first to gain complete understanding and control over the boot sequence on disk 1. And that, dear reader, is my question.