can i use hass.lo on am old computer. with some
help
You can if you can install a Linux distro (Ubuntu or Debian are preferred).
Then just follow the directions for installing hassio on a Linux system.
Or you can run normal home assistant in a Python virtual environment, or Docker.
Keep in mind that a desktop computer draws a fair bit of power (especially older models) and hass.io will need to be running 24/7/365. It adds up.
+1 on silvrr comment - worth it to just buy a RPi and dedicate it which should work for most deployments I would think.