Until today I had Windows XP in C: partition in dual-boot with Linux Mint. However today I tried to install Lubuntu, and while the installation was successful, I have access to all 3 OS on the GRUB menu, I lost my D: partition where I have some important files. It won't show on file explorers of Windows and Linux. However, it is recognized in gparted or Windows disk manager, as being totally used, but it still had some GB's of free space.
Both in Mint and Lubuntu I used the default options for partitioning, as far as I can tell, I think both of them took free space from the D: partition to make their ext4 partition. I'm afraid that if I try to recover the D: partition with testdisk utility, I might lose the GRUB menu and not boot at all.
How should I proceed to recover D: partition?