Would you happen to know what make, model, etc, the older machine is? (It's gonna be a wee bit awkward, I admit, since all those details are usually on a sticker on the back cover of the machine...)
Actually, upon examining the picture a bit more closely, it appears to be just one of the easy-access covers that's missing.....usually for accessing the RAM, HDD, etc.
But Windows never even noticed that I had installed Linux.
You were lucky. I did the same thing on a family member's machine (running Win 7), and it, too, never took any notice of Linux. This was, however, with legacy (MBR) BIOS. In many cases after installing Linux, people often find that Windows then refuses to boot, because GRUB has overwritten the Windows bootloader.....
In the early days of 14.04 (Trusty Tahr), they had a spell where the Ubuntu installer was actually wiping Windows right off the HDD when the 'dual-boot' option was selected. It wasn't all that long ago, either...
Edited by Mike_Walsh, 27 September 2016 - 10:56 AM.
Distros:- Multiple 'Puppies'..... and Anti-X 16.1
My Puppy BLOG ~~~ My Puppy PACKAGES
Compaq Presario SR1916UK; Athlon64 X2 3800+, 3 GB RAM, WD 500GB Caviar 'Blue', 32GB Kingspec PATA SSD, 3 TB Seagate 'Expansion' external HDD, ATI Radeon Xpress 200 graphics, Dell 15.1" pNp monitor (1024 x 768), TP-Link PCI-e USB 3.0 card, Logitech c920 HD Pro webcam, self-powered 7-port USB 2.0 hub
Dell Inspiron 1100; 2.6 GHz 400FSB P4, 1.5 GB RAM, 64GB KingSpec IDE SSD, Intel 'Extreme' graphics, 1 TB Seagate 'Expansion' external HDD, M$ HD-3000 'Lifecam'.