XP changes partition and hides/deletes Linux OS?

I have googled and tried to find related info to my dilemma to no avail. I hope someone reads this and recognizes a similar experience or knows what I'm talking about. Here's the scenario:

Primary Partition: Windows 2000
Extended Partition: NTFS partition
Logical partition: Linux distro
Logical Partition: Linux distro

Goal: To install Windows XP in the primary partition. Method: Use an open source/GNU partition manager to modify the partitions and give the primary partition enough space so that XP can be installed.

The spacing was something like?
Windows 2000 8GB
NTFS partition: 45 GB
Linux OS: 15 GB
Linux OS: 15 GB
Free space: remaining disk space

Anyway, my system is not here right now but what I have above is close to the disk arrangement. I'm posting using a different computer. To make a long story short, I arranged everything and made the primary position bigger. I created a partition there so that I had enough room to install XP. Therefore, Windows 2000 and XP would be in the primary partitions. I formatted the 'Drive' (Windows 2000 'sees' it as a drive although it is a partition) that XP would be installed in. I then install XP there. Everything seems okay so far.

But, when I boot up, Windows (the XP install, I suppose) has replaced the boot loader (was using GAG but I've used Grub as well before) with it's own boot loader. I try to use the live GAG CD to reinstall GAG and re-establish my partition scheme but GAG doesn't 'see' the Linux operating systems anymore. It's as though Windows has either deleted the Linux operating systems but what I thought was more likely, that they are not being seen or are invisible.

So, Windows XP has decided to 'dump' the Linux operating systems when it re-arranged or modified the drive (letter) arrangement.

Is there any way to bring back the Linux operating systems? Is there any chance they still might be there but are hidden or Windows XP has them but they're invisible?

I have read various guides and googled to no avail. I've read howtos for installing XP after a Linux OS is installed and vice versa (i.e. installing a Linux OS after XP is already installed. But, I haven't been able to find a scenario in which a Windows OS and a Linux OS is already installed but the user wants to install another Windows OS (but, obviously doesn't want to damage the existing Windows and Linux partitions and operating systems).

Any ideas? I really would like to know if it's at all possible to recover the Linux partitions or else I will have to install and would then have to accept that all the data and info is gone. :-(

What can/should I do? Thanks for any info and assistance.