demigaucher, what kind of filesystem are you using for your / and /boot (if it's a separate one) ?
The kernel is exactly the same during installation and when you're booting the installed system, so it can't be that. It's either something with a device whose driver was not included in the installation medium but it is now, or maybe something with the filesystem? Or else, it could be that the hard drive is faulty...
You have a problem with Salix? Post here and we'll do what we can to help.
What is the need to run v15.0 instead of what has made you happy? Do you need to go online with this machine you're trying to install Salix v15.0 on? If you want to use the latest, your hardware has to be able to keep up with it.
The 32-bit distros are still being offered but it becomes a real challenge for the older stuff done 15 years ago or earlier. Appreciate Slackware still being able to run, instead of doing it slowly, but because it's a limitation of the older equipment, not of the OS.
Besides Salix I have other penguins, including 32-bit Slackware with KDE Plasma and yes, it is slow but the important thing is that it runs. But I have Intel "Sandy Bridge" CPU which is "only" 10 years old with an internal HDD which is the real cause of the problem.
gapan already suggested you might have a problem with your hard disk. It might be a SMART failure. I suffered that on one of my computers last year and therefore had to force-boot with 32-bit Ubuntu Studio "Precise Pangolin" from an external USB disk. Another cause is having enough RAM. Having 2GB RAM or less really isn't enough anymore even for 32-bit. Otherwise the Linux kernel might not support your equipment any longer. Some of us should be glad Slackware and descendants haven't "officially" moved up to the v6 kernel yet because that's going to leave more equipment out in the cold.
Sadly, there are a few distros out there that could still work on old 32-bit machines but they seem to be based on Debian. Otherwise one has to settle for an OS which is not up to date and increasingly becomes a security risk using it online.