loading debian 10 on a very old compaq Presario dual boot

Had  three problems loading the Debian 10 iso (from a dvd I made)
1. the download script would not get past the step where it partitioned the disk until I used the menu option to format partition #3.
(I even waited whilst the script wrote 90 GB of zeroes on that drive, before discovering the format fix) 

2. The UUIDS in the grub .cfg file were changed (somehow) to where they were incorrct for my other linux kernel, although the UUIDS for debian were correct.  the /etc/fstab file for my other OS was adjusted to where the UUID entry were removed from that file, /etc/fstab for debian were correct and included swap)

3. Debian would crash on booting until I removed the boot=plainroot option from the debian vmlinux line in grub.cfg. (I also removed the quiet option) 

It's hard to help you when we don't know what you're doing, how you're doing it and why you're doing it.
It happens that the installer has a problem using a partition formatted in a different operating system or with specific programs. Then the actual solution is to tell him to format the partition in his own way.
The rest of your post has no sense and difficult to respond to.