installing Linux on an external disk still makes Win 7 unbootable w/o the external disk

I had that problem like 10 years ago already with other hardware and different Windows.

That computer does not come with a separate recovery medium, the recovery stuff is stored on its own 1st partition.
Once that problem will be fixed, it's possible to create a separate recovery medium, e.g. a 16 GB USB memory stick, from starting the computer using "F9".

Looks like I can't fix it with pure Windows means.

Will this fix it?!?

• Yast2 has a module called "Boot Loader Settings",
• there is a tab "Boot Loader Installation",
• there is a menu button "Other",
• there is an entry "Restore MBR of Hard Disk".